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  • richardmitnick 7:38 pm on October 23, 2014 Permalink | Reply
    Tags: , , Photon Sciences,   

    From BNL: “National Synchrotron Light Source II Achieves ‘First Light’” 

    Brookhaven Lab

    October 23, 2014
    Chelsea Whyte, (631) 344-8671 or Peter Genzer, (631) 344-3174

    The National Synchrotron Light Source II detects its first photons, beginning a new phase of the facility’s operations. Scientific experiments at NSLS-II are expected to begin before the end of the year.

    crowd
    A crowd gathered on the experimental floor of the National Synchrotron Light Source II to witness “first light,” when the x-ray beam entered a beamline for the first time at the facility.

    The brightest synchrotron light source in the world has delivered its first x-ray beams. The National Synchrotron Light Source II (NSLS-II) at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory achieved “first light” on October 23, 2014, when operators opened the shutter to begin commissioning the first experimental station (called a beamline), allowing powerful x-rays to travel to a phosphor detector and capture the facility’s first photons. While considerable work remains to realize the full potential of the new facility, first light counts as an important step on the road to facility commissioning.

    BNL NSLS II
    BNL NSLS-II Interior
    NSLS-II at BNL

    “This is a significant milestone for Brookhaven Lab, for the Department of Energy, and for the nation,” said Harriet Kung, DOE Associate Director of Science for Basic Energy Sciences. “The National Synchrotron Light Source II will foster new discoveries and create breakthroughs in crucial areas of national need, including energy security and the environment. This new U.S. user facility will advance the Department’s mission and play a leadership role in enabling and producing high-impact research for many years to come.”

    At 10:32 a.m. on October 23, a crowd of scientists, engineers, and technicians gathered around the Coherent Soft X-ray Scattering (CSX) beamline at NSLS-II, expectantly watching the video feed from inside a lead-lined hutch where the x-ray beam eventually struck the detector. As the x-rays hit the detector, cheers and applause rang out across the experimental hall for a milestone many years in the making.

    team
    The team of scientists, engineers, and technicians at the Coherent Soft X-ray Scattering (CSX) beamline gathered around the control station to watch as group leader Stuart Wilkins (seated, front) opened the shutter between the beamline and the storage ring, allowing x-rays to enter the first optical enclosure for the first time.

    “This achievement begins an exciting new chapter of synchrotron science at Brookhaven, building on the remarkable legacy of NSLS, and leading us in new directions we could not have imagined before,” said Laboratory Director Doon Gibbs. “It’s a great illustration of the ways that national labs continually evolve and grow to meet national needs, and it’s a wonderful time for all of us. Everyone at the Lab, in every role, supports our science, so we can all share in the sense of excitement and take pride in this accomplishment.”

    beam
    NSLS-II first x-rays
    Inside the beamline enclosure, a phosphor detector (the rectangle at right) captured the first x-rays (in white) which hit the mark dead center.

    In the heart of the 590,000 square foot facility, an electron gun emits packets of the negatively charged particles, which travel down a linear accelerator into a booster ring. There, the electrons are brought to nearly the speed of light, and then steered into the storage ring, where powerful magnets guide the beam on a half-mile circuit around the NSLS-II storage ring. As the electrons travel around the ring, they emit extremely intense x-rays, which are delivered and guided down beamlines into experimental end stations where scientists will carry out experiments for scientific research and discovery. NSLS-II accelerator operators have previously stored beam in the storage ring, but they hadn’t yet opened the shutters to allow x-ray light to reach a detector until today’s celebrated achievement.

    “We have been eagerly anticipating this culmination of nearly a decade of design, construction, and testing and the sustained effort and dedication of hundreds of individuals who made it possible,” said Steve Dierker, Associate Laboratory Director for Photon Sciences. ‘We have more work to do, but soon researchers from around the world will start using NSLS-II to advance their research on everything from new energy storage materials to developing new drugs to fight disease. I’m very much looking forward to the discoveries that NSLS-II will enable, and to the continuing legacy of groundbreaking synchrotron research at Brookhaven.”

    NSLS-II, a third-generation synchrotron light source, will be the newest and most advanced synchrotron facility in the world, enabling research not possible anywhere else. As a DOE Office of Science User Facility, it will offer researchers from academia, industry, and national laboratories new ways to study material properties and functions with nanoscale resolution and exquisite sensitivity by providing state-of-the-art capabilities for x-ray imaging, scattering, and spectroscopy.

    Currently 30 beamlines are under development to take advantage of the high brightness of the x-rays at NSLS-II. Commissioning of the first group of seven beamlines will begin in the coming months, with first experiments beginning at the CSX beamline before the end of 2014.

    At the NSLS-II beamlines, scientists will be able to generate images of the structure of materials such as lithium-ion batteries or biological proteins at the nanoscale level—research expected to advance many fields of science and impact people’s quality of life in the years to come.

    NSLS-II will support the Department of Energy’s scientific mission by providing the most advanced tools for discovery-class science in condensed matter and materials science, physics, chemistry, and biology—science that ultimately will enhance national and energy security and help drive abundant, safe, and clean energy technologies.

    Media Contacts:
    Karen McNulty Walsh, 631 344-8350 or kmcnulty@bnl.gov
    Chelsea Whyte, 631 344-8671 or cwhyte@bnl.gov

    See the full article here.

    BNL Campus

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 6:22 am on October 21, 2014 Permalink | Reply
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    From SLAC: “Puzzling New Behavior Found in High-Temperature Superconductors” 


    SLAC Lab

    October 20, 2014

    Ultimate Goal: A Super-efficient Way to Conduct Electricity at Room Temperature

    Research by an international team led by SLAC and Stanford scientists has uncovered a new, unpredicted behavior in a copper oxide material that becomes superconducting – conducting electricity without any loss – at relatively high temperatures.

    This new phenomenon – an unforeseen collective motion of electric charges coursing through the material – presents a challenge to scientists seeking to understand its origin and connection with high-temperature superconductivity. Their ultimate goal is to design a superconducting material that works at room temperature.

    “Making a room-temperature superconductor would save the world enormous amounts of energy,” said Thomas Devereaux, leader of the research team and director of the Stanford Institute for Materials and Energy Sciences (SIMES), which is jointly run with SLAC. “But to do that we must understand what’s happening inside the materials as they become superconducting. This result adds a new piece to this long-standing puzzle.”

    The results are published Oct. 19 in Nature Physics.

    Delving Into Doping Differences

    The researchers used an emerging X-ray technique called resonant inelastic X-ray scattering, or RIXS, to measure how the properties of a copper oxide change as extra electrons are added in a process known as doping. The team used the Swiss Light Source’s RIXS instrument, which currently has the world’s highest resolution and can reveal atomic-scale excitations – rapid changes in magnetism, electrical charge and other properties – as they move through the material.

    Copper oxide, a ceramic that normally doesn’t conduct electricity at all, becomes superconducting only when doped with other elements to add or remove electrons and chilled to low temperatures. Intriguingly, the electron-rich version loses its superconductivity when warmed to about 30 degrees above absolute zero (30 kelvins) while the electron-poor one remains superconducting up to 120 kelvins (minus 244 degrees Fahrenheit). One of the goals of the new research is to understand why they behave so differently.

    The experiments revealed a surprising increase of magnetic energy and the emergence of a new collective excitation in the electron-rich compounds, said Wei-sheng Lee, a SLAC staff scientist and lead author on the Nature Physics paper. “It’s very puzzling that these new electronic phenomena are not seen in the electron-poor material,” he said.

    wl
    SLAC Staff Scientist Wei-sheng Lee (SLAC National Accelerator Laboratory)

    Lee added that it’s unclear whether the new collective excitation is related to the ability of electrons to pair up and effortlessly conduct electricity – the hallmark of superconductivity – or whether it promotes or limits high-temperature superconductivity. Further insight can be provided by additional experiments using next-generation RIXS instruments that will become available in a few years at synchrotron light sources worldwide.

    A Long, Tortuous Path

    This discovery is the latest step in the long and tortuous path toward understanding high-temperature superconductivity.

    Scientists have known since the late 1950s why certain metals and simple alloys become superconducting when chilled within a few degrees of absolute zero: Their electrons pair up and ride waves of atomic vibrations that act like a virtual glue to hold the pairs together. Above a certain temperature, however, the glue fails as thermal vibrations increase, the electron pairs split up and superconductivity disappears.

    Starting in 1986, researchers discovered a number of materials that are superconducting at higher temperatures. By understanding and optimizing how these materials work, they hope to develop superconductors that work at room temperature and above.

    Until recently, the most likely glue holding superconducting electron pairs together at higher temperatures seemed to be strong magnetic excitations created by interactions between electron spins. But a recent theoretical simulation by SLAC and Stanford researchers concluded that these high-energy magnetic interactions are not the sole factor in copper oxide’s high-temperature superconductivity. The new results confirm that prediction, and also complement a 2012 report on the behavior of electron-poor copper oxides by a team that included Lee, Devereaux and several other SLAC/Stanford scientists.

    “Theorists must now incorporate this new ingredient into their explanations of how high-temperature superconductivity works,” said Thorsten Schmitt, leader of the RIXS team at the Paul Scherrer Institute in Switzerland, who collaborated on the study.

    Other researchers involved in the study were from Columbia University, University of Minnesota, AGH University of Science and Technology in Poland, National Synchrotron Radiation Research Center and National Tsing Hua University in Taiwan, and the Chinese Academy of Sciences. Funding for the research came from the DOE Office of Science, U.S. National Science Foundation and Swiss National Science Foundation.

    See the full article, with animation video, here.

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 5:03 pm on September 10, 2014 Permalink | Reply
    Tags: , , , Photon Sciences,   

    From LBL: “Advanced Light Source Sets Microscopy Record” 

    Berkeley Logo

    Berkeley Lab

    September 10, 2014
    Lynn Yarris (510) 486-5375

    A record-setting X-ray microscopy experiment may have ushered in a new era for nanoscale imaging. Working at the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab), a collaboration of researchers used low energy or “soft” X-rays to image structures only five nanometers in size. This resolution, obtained at Berkeley Lab’s Advanced Light Source (ALS), a DOE Office of Science User Facility, is the highest ever achieved with X-ray microscopy.

    LBL Advanced Light Source
    LBL ALS

    image
    Ptychographic image using soft X-rays of lithium iron phosphate nanocrystal after partial dilithiation. The delithiated region is shown in red.

    Using ptychography, a coherent diffractive imaging technique based on high-performance scanning transmission X-ray microscopy (STXM), the collaboration was able to map the chemical composition of lithium iron phosphate nanocrystals after partial dilithiation. The results yielded important new insights into a material of high interest for electrochemical energy storage.

    “We have developed diffractive imaging methods capable of achieving a spatial resolution that cannot be matched by conventional imaging schemes,” says David Shapiro, a physicist with the ALS. “We are now entering a stage in which our X-ray microscopes are no longer limited by our optics and we can image at nearly the wavelength of our X-ray light.”

    Shapiro is the lead and corresponding author of a paper reporting this research in Nature Photonics. The paper is titled “Chemical composition mapping with nanometer resolution by soft X-ray microscopy.” (See below for a full list of co-authors and their affiliations.)

    ds
    David Shapiro with the STXM instruments at ALS beamline 5.3.2.1. (Photo by Roy Kaltschmidt)

    In ptychography (pronounced tie-cog-raphee), a combination of multiple coherent diffraction measurements is used to obtain 2D or 3D maps of micron-sized objects with high resolution and sensitivity. Because of the sensitivity of soft x-rays to electronic states, ptychography can be used to image chemical phase transformations and the mechanical consequences of those transformations that a material undergoes.

    “Until this work, however, the spatial resolution of ptychographic microscopes did not surpass that of the best conventional systems using X-ray zone plate lenses,” says Howard Padmore, leader of the Experimental Systems Group at the ALS and a co-author of the Nature Photonics paper. “The problem stemmed from the fact that ptychography was primarily developed on hard X-ray sources using simple pinhole optics for illumination. This resulted in a low scattering cross-section and low coherent intensity at the sample, which meant that exposure times had to be extremely long, and that mechanical and illumination stabilities were not good enough for high resolution.”

    Key to the success of Shapiro, and his collaborators were the use of soft X-rays which have wavelengths ranging between 1 to 10 nanometers, and a special algorithm that eliminated the effect of all incoherent background signals. Ptychography measurements were recorded with the STXM instruments at ALS beamline 11.0.2, which uses an undulator x-ray source, and ALS beamline 5.3.2.1, which uses a bending magnet source. A coherent soft X-ray beam would be focused onto a sample and scanned in 40 nanometer increments. Diffraction data would then be recorded on an X-ray CCD (charge-coupled device) that allowed reconstruction of the sample to very high spatial resolution.

    “Throughout the ptychography scans, we maintained the sample and focusing optic in relative alignment using an interferometric feedback system with a precision comparable to the wavelength of the X-ray illumination,” Shapiro says.

    Lithium iron phosphate is widely studied for its use as a cathode material in rechargeable lithium-ion batteries. In using their ptychography technique to map the chemical composition of lithium iron phosphate crystals, Shapiro and his collaborators found a strong correlation between structural defects and chemical phase propagation.

    “Surface cracking in these crystals was expected,” Shapiro says, “but there is no other means of visualizing the correlation of those cracks with chemical composition at these scales. The ability to visualize the coupling of the kinetics of a phase transformation with the mechanical consequences is critical to designing materials with ultimate durability.”

    Shapiro and his colleagues have already begun applying their ptychography technique to the study of catalytic and magnetic films, magnetotactic bacteria, polymer blends and green cements.
    In this soft X-ray ptychography set-up, a 60 nm width outer-zone-plate focuses a coherent soft X-ray beam onto the sample, which is scanned in 40 nm increments to ensure overlap of the probed areas.

    In this soft X-ray ptychography set-up, a 60 nm width outer-zone-plate focuses a coherent soft X-ray beam onto the sample, which is scanned in 40 nm increments to ensure overlap of the probed areas.

    For the chemical mapping of lithium iron phosphate they used the STXM instrument at ALS beamline 5.3.2.1 which required up to 800 milliseconds of exposure to the X-ray beam for each scan. Next year, they anticipate using a new ALS beamline called COSMIC (COherent Scattering and MICroscopy), which will feature a high brightness undulator x-ray source coupled to new high-frame-rate CCD sensors that will cut beam exposure times to only a few milliseconds and provide spatial resolution at the wavelength of the radiation.

    image2
    In this soft X-ray ptychography set-up, a 60 nm width outer-zone-plate focuses a coherent soft X-ray beam onto the sample, which is scanned in 40 nm increments to ensure overlap of the probed areas. – See more at: http://newscenter.lbl.gov/2014/09/10/advanced-light-source-sets-microscopy-record/#sthash.6DLMbCxp.dpuf

    “If visible light microscopes could only achieve a resolution that was 50 times the wavelength of visible light, we would not be able to see most single celled organisms,” Shapiro says. “Where would the life sciences be with such a limitation? We are now approaching the point where we will have X-ray microscopes of comparable quality to today’s visible light instruments for the study of nanomaterials.”

    Co-authoring the Nature Photonics paper in addition to Shapiro and Padmore were Young-Sang Yu, Tolek Tyliszczak, Jordi Cabana, Rich Celestre, Weilun Chao, David Kilcoyne, Stefano Marchesini, Tony Warwick and Lee Yang of Berkeley Lab; Konstantin Kaznatcheev of Brookhaven National Laboratory; Shirley Meng of the University of San Diego; and Filipe Maia of Uppsala University in Sweden.

    This research was primarily supported by the DOE Office of Science.

    See the full article here.

    A U.S. Department of Energy National Laboratory Operated by the University of California

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  • richardmitnick 12:59 pm on September 9, 2014 Permalink | Reply
    Tags: , , Photon Sciences, ,   

    From SLAC: “Buckyballs and Diamondoids Join Forces in Tiny Electronic Gadget” 


    SLAC Lab

    September 9, 2014
    Press Office Contact: Andrew Gordon, agordon@slac.stanford.edu, (650) 926-2282

    Scientists Craft Two Exotic Forms of Carbon into a Molecule for Steering Electron Flow

    Scientists have married two unconventional forms of carbon – one shaped like a soccer ball, the other a tiny diamond – to make a molecule that conducts electricity in only one direction. This tiny electronic component, known as a rectifier, could play a key role in shrinking chip components down to the size of molecules to enable faster, more powerful devices.

    dd
    An international team led by researchers at SLAC National Accelerator Laboratory and Stanford University joined two offbeat carbon molecules – diamondoids, the square cages at left, and buckyballs, the soccer-ball shapes at right – to create “buckydiamondoids,” center. These hybrid molecules function as rectifiers, conducting electrons in only one direction, and could help pave the way to molecular electronic devices. (Manoharan Lab/Stanford University)

    “We wanted to see what new, emergent properties might come out when you put these two ingredients together to create a ‘buckydiamondoid,’” said Hari Manoharan of the Stanford Institute for Materials and Energy Sciences (SIMES) at the Department of Energy’s SLAC National Accelerator Laboratory. “What we got was a basically a one-way valve for conducting electricity – clearly more than the sum of its parts.”

    The research team, which included scientists from Stanford University, Belgium, Germany and Ukraine, reported its results September 9, 2014, in Nature Communications.

    Two Offbeat Carbon Characters Meet Up

    Many electronic circuits have three basic components: a material that conducts electrons; rectifiers, which commonly take the form of diodes, to steer that flow in a single direction; and transistors to switch the flow on and off. Scientists combined two offbeat ingredients – buckyballs and diamondoids – to create the new diode-like component.

    Buckyballs – short for buckminsterfullerenes – are hollow carbon spheres whose 1985 discovery earned three scientists a Nobel Prize in chemistry. Diamondoids are tiny carbon cages bonded together as they are in diamonds, but weighing less than a billionth of a billionth of a carat. Both are subjects of a lot of research aimed at understanding their properties and finding ways to use them.

    In 2007, a team led by researchers from SLAC and Stanford discovered that a single layer of diamondoids on a metal surface can efficiently emit a beam of electrons. Manoharan and his colleagues wondered: What would happen if they paired an electron-emitting diamondoid with another molecule that likes to grab electrons? Buckyballs are just that sort of electron-grabbing molecule.

    A Very Small Valve for Channeling Electron Flow

    For this study, diamondoids were produced in the SLAC laboratory of SIMES researchers Jeremy Dahl and Robert Carlson, who are world experts in extracting the tiny diamonds from petroleum. They were then shipped to Germany, where chemists at Justus-Liebig University figured out how to attach them to buckyballs.

    The resulting buckydiamondoids, which are just a few nanometers long, were tested in SIMES laboratories at Stanford. A team led by graduate student Jason Randel and postdoctoral researcher Francis Niestemski used a scanning tunneling microscope to make images of the hybrid molecules and measure their electronic behavior. They discovered the hybrid is an excellent rectifier: The electrical current flowing through the molecule was up to 50 times stronger in one direction, from electron-spitting diamondoid to electron-catching buckyball, than in the opposite direction. This is something neither component can do on its own.

    ball
    An image made with a scanning tunneling microscope shows hybrid buckydiamondoid molecules on a gold surface. The buckyball end of each molecule is attached to the surface, with the diamondoid end sticking up; both are clearly visible. The area shown here is 5 nanometers on a side. (H. Manoharan et al, Nature Communications)

    image
    Illustration of a buckydiamondoid molecule under a scanning tunneling microscope (STM). The sharp metallic tip of the STM ends in a single atom; as it scans over a sample, electrons tunnel from the tip into the sample. In this study the STM made images of the buckydiamondoids and probed their electronic properties. (SLAC National Accelerator Laboratory)

    While this is not the first molecular rectifier ever invented, it’s the first one made from just carbon and hydrogen, a simplicity researchers find appealing, said Manoharan, who is an associate professor of physics at Stanford. The next step, he said, is to see if transistors can be constructed from the same basic ingredients.

    “Buckyballs are easy to make – they can be isolated from soot – and the type of diamondoid we used here, which consists of two tiny cages, can be purchased commercially,” he said. “And now that our colleagues in Germany have figured out how to bind them together, others can follow the recipe. So while our research was aimed at gaining fundamental insights about a novel hybrid molecule, it could lead to advances that help make molecular electronics a reality.”

    Other research collaborators came from the Catholic University of Louvain in Belgium and Kiev Polytechnic Institute in Ukraine. The primary funding for the work came from the U.S. Department of Energy Office of Science.

    See the full article here.

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 5:33 am on August 16, 2014 Permalink | Reply
    Tags: , , , , Photon Sciences,   

    From Brookhaven Lab: “Harnessing the Power of Bacteria’s Sophisticated Immune System” 

    Brookhaven Lab

    August 15, 2014
    Karen McNulty Walsh, (631) 344-8350 or Peter Genzer, (631) 344-3174

    Researchers Now Better Understand How Bacteria Can So Quickly Protect Itself From Harm, Could Help Unlock Clues About Antibiotic Resistance

    Bacteria’s ability to destroy viruses has long puzzled scientists, but researchers at the Johns Hopkins Bloomberg School of Public Health say they now have a clear picture of the bacterial immune system and say its unique shape is likely why bacteria can so quickly recognize and destroy their assailants.

    The researchers drew what they say is the first-ever picture of the molecular machinery, known as Cascade, which stands guard inside bacterial cells. To their surprise, they found it contains a two-strand, unencumbered structure that resembles a ladder, freeing it to do its work faster than a standard double-helix would allow.

    The findings, published online Aug. 14 in the journal Science, may also provide clues about the spread of antibiotic resistance, which occurs when bacteria adapt to the point where antibiotics no longer work in people who need them to treat infections, since similar processes are in play. The World Health Organization (WHO) considers antibiotic resistance a major threat to public health around the world.

    “If you understand what something looks like, you can figure out what it does,” says study leader Scott Bailey, PhD, an associate professor in the Bloomberg School’s Department of Biochemistry and Molecular Biology. “And here we found a structure that nobody’s ever seen before, a structure that could explain why Cascade is so good at what it does.”

    For their study, Bailey and his colleagues used something called X-ray crystallography to draw the picture of Cascade, a key component of bacteria’s sophisticated immune system known as CRISPR, an acronym for Clustered Regularly Interspaced Short Palindromic Repeats. Cascade uses the information housed in sequences of RNA as shorthand to identify foreign invaders and kill them.

    crispr
    Diagram of the possible mechanism for CRISPR

    Much of the human immune system is well understood, but until recently scientists didn’t realize the level of complexity associated with the immune system of single-cell life forms, including bacteria. Scientists first identified CRISPR several years ago when trying to understand why bacterial cultures used to make yogurt succumbed to viral infections. Researchers subsequently discovered they could harness the CRISPR bacterial immune system to edit DNA and repair damaged genes. One group, for example, was able to remove viral DNA from human cells infected with HIV.

    Bailey’s work is focused on how Cascade is able to help bacteria fight off viruses called bacteriophages. The Cascade system uses short strands of bacterial RNA to scan the bacteriophage DNA to see if it is foreign or self. If foreign, the cell launches an attack that chews up the invading bacteriophage.

    bac
    The structure of a typical myovirus bacteriophage

    To “see” how this happens, Bailey and his team converted Cascade into a crystalized form. Technicians at the National Synchrotron Light Source at Brookhaven National Laboratory in Upton, New York, and the Stanford Synchrotron Radiation Lightsource then trained high-powered X-rays on the crystals. The X-rays provided computational data to the Bloomberg School scientists allowing them to draw Cascade, an 11-protein machine that only operates if each part is in perfect working order.

    Brookhaven NSLS
    Brookhaven NSLS

    SLAC SSRL
    SLAC SSRL

    What they saw was unexpected. Instead of the RNA and DNA wrapping around each other to form what is known as a double-helix structure, in Cascade the DNA and RNA are more like parallel lines, forming something of a ladder. Bailey says that if RNA had to wrap itself around DNA to recognize an invader – and then unwrap itself to look at the next strand – the process would take too much time to ward off infection. With a ladder structure, RNA can quickly scan DNA.

    ah
    Annie Heroux at NSLS

    In the new study, Bailey says his team determined that the RNA scans the DNA in a manner similar to how humans scan text for a key word. They break long stretches of characters into smaller bite-sized segments, much like words themselves, so they can be spotted more easily.

    Since the CRISPR-Cas system naturally acts as a barrier to the exchange of genetic information between bacteria and bacteriophages, its function can offer clues to how antibiotic resistance develops and ideas for how to keep it from happening.

    “We’re finding more pieces to the puzzle,” Bailey says. “This gives us a better understanding of how these machines find their targets, which may help us harness the CRISPR system as a tool for therapy or manipulation of DNA in a lab setting. And it all started when someone wanted to make yogurt more cheaply.”

    “Crystal structure of a CRISPR RNA-guided surveillance complex bound to a ssDNA target” was written by Sabin Mulepati, Annie Heroux and Scott Bailey.

    This work was funded by a grant from the National Institute of Health’s National Institute of General Medical Sciences (GM097330).

    See the full article here.

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 11:44 am on August 1, 2014 Permalink | Reply
    Tags: , , , , Photon Sciences,   

    From M.I.T.: “Light pulses control graphene’s electrical behavior” 


    M.I.T.

    July 31, 2014
    David L. Chandler | MIT News Office

    Graphene, an ultrathin form of carbon with exceptional electrical, optical, and mechanical properties, has become a focus of research on a variety of potential uses. Now researchers at MIT have found a way to control how the material conducts electricity by using extremely short light pulses, which could enable its use as a broadband light detector.

    graphene
    Researchers at MIT have found a way to control how graphene conducts electricity by using extremely short light pulses. In this illustration, a lattice of graphene is shown with its bonds (bars) connecting carbon atoms (balls). When the light pulse hits the atoms, electrons can accumulate or diminish in number. By controlling the concentration of electrons in a graphene sheet, researchers can change the material’s electrical conductivity.

    Illustration: Jose-Luis Olivares/MIT

    The new findings are published in the journal Physical Review Letters, in a paper by graduate student Alex Frenzel, Nuh Gedik, and three others.

    The researchers found that by controlling the concentration of electrons in a graphene sheet, they could change the way the material responds to a short but intense light pulse. If the graphene sheet starts out with low electron concentration, the pulse increases the material’s electrical conductivity. This behavior is similar to that of traditional semiconductors, such as silicon and germanium.

    But if the graphene starts out with high electron concentration, the pulse decreases its conductivity — the same way that a metal usually behaves. Therefore, by modulating graphene’s electron concentration, the researchers found that they could effectively alter graphene’s photoconductive properties from semiconductorlike to metallike.

    The finding also explains the photoresponse of graphene reported previously by different research groups, which studied graphene samples with differing concentration of electrons. “We were able to tune the number of electrons in graphene, and get either response,” Frenzel says.

    To perform this study, the team deposited graphene on top of an insulating layer with a thin metallic film beneath it; by applying a voltage between graphene and the bottom electrode, the electron concentration of graphene could be tuned. The researchers then illuminated graphene with a strong light pulse and measured the change of electrical conduction by assessing the transmission of a second, low-frequency light pulse.

    In this case, the laser performs dual functions. “We use two different light pulses: one to modify the material, and one to measure the electrical conduction,” Gedik says, adding that the pulses used to measure the conduction are much lower frequency than the pulses used to modify the material behavior. To accomplish this, the researchers developed a device that was transparent, Frenzel explains, to allow laser pulses to pass through it.

    This all-optical method avoids the need for adding extra electrical contacts to the graphene. Gedik, the Lawrence C. and Sarah W. Biedenharn Associate Professor of Physics, says the measurement method that Frenzel implemented is a “cool technique. Normally, to measure conductivity you have to put leads on it,” he says. This approach, by contrast, “has no contact at all.”

    Additionally, the short light pulses allow the researchers to change and reveal graphene’s electrical response in only a trillionth of a second.

    In a surprising finding, the team discovered that part of the conductivity reduction at high electron concentration stems from a unique characteristic of graphene: Its electrons travel at a constant speed, similar to photons, which causes the conductivity to decrease when the electron temperature increases under the illumination of the laser pulse. “Our experiment reveals that the cause of photoconductivity in graphene is very different from that in a normal metal or semiconductor,” Frenzel says.

    The researchers say the work could aid the development of new light detectors with ultrafast response times and high sensitivity across a wide range of light frequencies, from the infrared to ultraviolet. While the material is sensitive to a broad range of frequencies, the actual percentage of light absorbed is small. Practical application of such a detector would therefore require increasing absorption efficiency, such as by using multiple layers of graphene, Gedik says.

    Isabella Gierz, a professor at the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, who was not involved in this research, says, “The work is interesting because it presents a systematic study of the doping dependence of the low-energy dynamics, which has not received much attention so far.” She says the new research “certainly helps to reconcile previous apparently contradicting results,” and adds that these findings represent “a solid experiment, analysis, and interpretation.”

    The research team also included Jing Kong, the ITT Career Development Associate Professor of Electrical Engineering at MIT, who provided the graphene samples used for the experiments; physics postdoc Chun Hung Lui; and Yong Cheol Shin, a graduate student in materials science and engineering. The work received support from the U.S. Department of Energy and the National Science Foundation.

    See the full article here.


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  • richardmitnick 11:28 am on July 28, 2014 Permalink | Reply
    Tags: , , , Photon Sciences   

    From Brookhaven Lab: “Understanding the Source of Extra-large Capacities in Promising Li-ion Battery Electrodes” 

    Brookhaven Lab

    July 28, 2014
    Laura Mgrdichian

    Lithium (Li) ion batteries power almost all of the portable electronic devices that we use everyday, including smart phones, cameras, toys, and even electric cars. Researchers across the globe are working to find materials that will lead to safe, cheap, long-lasting, and powerful Li-ion batteries.

    Working at various U.S. Department of Energy light source facilities and at Cambridge and Stony Brook universities, a group of researchers recently studied a class of Li-ion battery electrodes that have capacities much greater than those of the materials used in today’s batteries. The researchers wanted to determine why these materials can often store more charge than theory predicts.

    path
    A summary of the three-stage reaction pathway of the ruthenium-oxide-lithium battery system.

    The authors chose ruthenium oxide (RuO2) as a model system to study these so-called “conversion materials,” named because they undergo large structural changes when reacting with lithium ions, reversibly forming metal nanoparticles and salts (here Ru and Li2O). These reactions are very different from those that occur in conventional electrodes, which store charge by allowing Li ions to nestle into spaces within the crystal lattice.

    “Our investigation identified the source of the additional capacity found for RuO2, and has also yielded a protocol for studying the ‘passivation layer’ that forms on battery electrodes, which protects the electrolyte from undergoing further decomposition reactions in subsequent charge-discharge cycles,” said the study’s corresponding researcher, Clare Grey, a professor in the chemistry departments at Cambridge and Stony Brook universities. “Understanding the structures of these passivation layers is key to making batteries that last long enough for use in applications such as transportation and power-grid storage.”

    At Brookhaven National Laboratory’s National Synchrotron Light Source, the team studied their samples using x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS). At the Advanced Photon Source at Argonne National Laboratory, they used two additional techniques, high-resolution x-ray diffraction (XRD) and scattering pair distribution function (PDF) analysis, to extract information on the electronic and long/short-range structural changes of the RuO2 electrode in real time as the battery was discharged and charged. Using these methods, the team showed that RuO2 was reduced to Ru nanoparticles and Li2O via the formation of intermediate phases, LixRuO2.

    Since this did not explain the source of the additional charge-storage mechanism, the group used another technique, high-resolution solid-state nuclear magnetic resonance (NMR). This method involves subjecting a sample to a magnetic field and measuring the response of the nuclei within the sample. It can yield specific information on the chemical compositions and local structures, and is particularly useful for studying compounds that contain only “light” elements, such as hydrogen (H), Li, and oxygen (O), which are difficult to detect using XRD. The NMR data showed that the major contributor to the capacity is the formation of LiOH, which reversibly converts to Li2O and LiH. Minor contributors to the capacity come from Li storage on the Ru nanoparticle surfaces, forming a LixRu alloy, and the decomposition of the electrolyte. The latter, however, ultimately causes the capacity to diminish and will result in the death of the battery following multiple charge cycles.

    Scientists from the University of Cambridge, Brookhaven National Laboratory, Argonne National Laboratory, and Stony Brook University conducted this research. It was published in the December 2013 issue of Nature Materials, 12, 1130-1136. The paper is titled Origin of additional capacities in metal oxide lithium-ion battery electrodes, and the authors are Yan-Yan Hu, Zigeng Liu, Kyung-Wan Nam, Olaf J. Borkiewicz, Jun Cheng, Xiao Hua, Matthew T. Dunstan, Xiqian Yu, Kamila M. Wiaderek, Lin-Shu Du, Karena W. Chapman, Peter J. Chupas, Xiao-Qing Yang and Clare P. Grey.

    See the full article here.

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 10:57 am on July 9, 2014 Permalink | Reply
    Tags: , , , Photon Sciences   

    From Brookhaven Lab: “NSLS-II Reaches 25 Milliamps of Current with New Superconducting RF Cavity” 

    Brookhaven Lab

    July 9, 2014
    Chelsea Whyte

    In the early evening of July 2, 2014, the National Synchrotron Light Source II (NSLS-II) at the U.S. Department of Energy’s Brookhaven National Laboratory reached 25 milliamps of current at 3 GeV (3 billion electron volts) using a new superconducting radio-frequency (SRF) cavity.

    Brookhaven NSLS II Photo
    NSLS II campus

    The milestone was reached “thanks to enormous efforts by everybody in the last two months,” according to Accelerator Division Director Ferdinand Willeke in the Photon Sciences Directorate.

    The accelerator commissioning team achieved this significant milestone by completing several major tasks, which included installing a superconducting RF cavity in the storage ring and making it serviceable by operating a new cryogenic plant.

    In addition, the team installed several other important components, including two in-vacuum undulators in the storage ring; collimators mounted on the ratchet wall; and personal protection systems at beamline front-ends, where x-rays will exit the ring and enter the beam lines.

    25
    25 milliamps of current at 3GeV Just before 5:30 p.m. on July 2, 2014, the storage ring at the National Synchrotron Light Source II — outfitted with new a superconducting radio-frequency cavity — held 25 milliamps of current at 3GeV, a major milestone in the commissioning of the state-of-the-art facility.

    Radio-frequency (RF) group leader Jim Rose added, “With the help of the riggers and the support of the vacuum and cryogenics group, we installed the cavity into the NSLS-II tunnel. Then we cooled it down to 4.5 degrees Kelvin, where it becomes superconducting. After conditioning the cavity to 1.2 megavolts, we turned it over to operations, and the accelerator physicists quickly achieved the 25-milliamp objective of this commissioning run.”

    Advanced Energy Systems in Medford, NY, built the SRF cavity, their first of two superconducting cavities for NSLS-II.

    The second cavity and other hardware are still to be installed before the accelerator reaches full design current of 500 milliamps, according to deputy division director Timur Shaftan.

    “The intensity will come up little by little over the next few years,” Shaftan said. The next step is commissioning of insertion devices and front-ends, he said.

    When completed, NSLS-II will be a state-of-the-art, medium-energy electron storage ring that produces x-rays up to 10,000 times brighter than the original NSLS, which started operating at Brookhaven National Lab in 1982 and is shutting down at the end of September 2014.

    NSLS-II construction began in 2009, with a $912-million budget from the U.S. Department of Energy Office of Science. Construction has passed through distinct phases, starting with conventional construction of the ring building and laboratory-office buildings, and later installation of the accelerator and beamlines. Back in April 2014, accelerator physicists and operators achieved 25 milliamps of current at 3 GeV in the storage ring using a non-superconducting cavity. The final NSLS-II design calls for SRF cavities, however, and so the current milestone was key to final commissioning of the storage ring.

    Progress on the facility continues, with an initial suite of beamlines for early science expected to be commissioned in the coming months.

    DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

    See the full article here.

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 9:18 am on June 27, 2014 Permalink | Reply
    Tags: Atomic Physics, , , , Photon Sciences,   

    From Berkeley Lab: “Not Much Force: Berkeley Researchers Detect Smallest Force Ever Measured” 


    Berkeley Lab

    June 26, 2014
    Lynn Yarris

    What is believed to be the smallest force ever measured has been detected by researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley. Using a combination of lasers and a unique optical trapping system that provides a cloud of ultracold atoms, the researchers measured a force of approximately 42 yoctonewtons. A yoctonewton is one septillionth of a newton and there are approximately 3 x 1023 yoctonewtons in one ounce of force.

    plumb
    Mechanical oscillators translate an applied force into measureable mechanical motion. The Standard Quantum Limit is imposed by the Heisenberg uncertainty principle, in which the measurement itself perturbs the motion of the oscillator, a phenomenon known as “quantum back-action.” (Image by Kevin Gutowski)

    “We applied an external force to the center-of-mass motion of an ultracold atom cloud in a high-finesse optical cavity and measured the resulting motion optically,” says Dan Stamper-Kurn, a physicist who holds joint appointments with Berkeley Lab’s Materials Sciences Division and the UC Berkeley Physics Department. “When the driving force was resonant with the cloud’s oscillation frequency, we achieved a sensitivity that is consistent with theoretical predictions and only a factor of four above the Standard Quantum Limit, the most sensitive measurement that can be made.”

    Stamper-Kurn is the corresponding author of a paper in Science that describes these results. The paper is titled Optically measuring force near the standard quantum limit. Co-authors are Sydney Schreppler, Nicolas Spethmann, Nathan Brahms, Thierry Botter and Maryrose Barrios.

    If you want to confirm the existence of gravitational waves, space-time ripples predicted by Albert Einstein in his theory of general relativity, or want to determine to what extent the law of gravity on the macroscopic scale, as described by Sir Isaac Newton, continues to apply at the microscopic scale, you need to detect and measure forces and motions that are almost incomprehensively tiny. For example, at the Laser Interferometer Gravitational-Wave Observatory (LIGO), scientists are attempting to record motions as small as one thousandth the diameter of a proton.

    sk
    From left, Sydney Schreppler, Dan Stamper-Kurn and Nicolas Spethmann were part of a team that detected the smallest force ever measured using a unique optical trapping system that provides ultracold atoms. (Photo by Roy Kaltschmidt)

    At the heart of all ultrasensitive detectors of force are mechanical oscillators, systems for translating an applied force into measureable mechanical motion. As measurements of force and motion reach quantum levels in sensitivity, however, they bump up against a barrier imposed by the Heisenberg uncertainty principle, in which the measurement itself perturbs the motion of the oscillator, a phenomenon known as “quantum back-action.” This barrier is called the Standard Quantum Limit (SQL). Over the past couple of decades, a wide array of strategies have been deployed to minimize quantum back-action and get ever closer to the SQL, but the best of these techniques fell short by six to eight orders of magnitude.

    “We measured force with a sensitivity that is the closest ever to the SQL,” says Sydney Schreppler, a member of the Stamper-Kurn research group and lead author of the Science paper. “We were able to achieve this sensitivity because our mechanical oscillator is composed of only 1,200 atoms.”

    In the experimental set-up used by Schreppler, Stamper-Kurn and their colleagues, the mechanical oscillator element is a gas of rubidium atoms optically trapped and chilled to nearly absolute zero. The optical trap consists of two standing-wave light fields with wavelengths of 860 and 840 nanometers that produce equal and opposite axial forces on the atoms. Center-of-mass motion is induced in the gas by modulating the amplitude of the 840 nanometer light field. The response is measured using a probe beam with a wavelength of 780 nanometers.

    graph
    To measure force, a cloud of atoms (gray oval) are trapped in an optical cavity created by two standing-wave light fields, ODT A and ODT B. The amplitude of ODT B is varied to create a force that is optomechanically transduced onto the phase of a probe light for measurement. No image credit.

    “When we apply an external force to our oscillator it is like hitting a pendulum with a bat then measuring the reaction,” says Schreppler. “A key to our sensitivity and approaching the SQL is our ability to decouple the rubidium atoms from their environment and maintain their cold temperature. The laser light we use to trap our atoms isolates them from external environmental noise but does not heat them, so they can remain cold and still enough to allow us to approach the limits of sensitivity when we apply a force.”

    Schreppler says it should be possible to get even closer to the SQL for force sensitivity through a combination of colder atoms and improved optical detection efficiency. She also says there are back-action evading techniques that can be taken by performing non-standard measurements. For now, the experimental approach demonstrated in this study provides a means by which scientists trying to detect gravitational waves can compare the limits of their detection abilities to the predicted amplitude and frequency of gravitational waves. For those seeking to determine whether Newtonian gravity applies to the quantum world, they now have a way to test their theories. The enhanced force-sensitivity in this experiment could also point the way to improved atomic force microscopy.

    “A scientific paper in 1980 predicted that the SQL might be reached within five years,” Schreppler says. “It took about 30 years longer than predicted, but we now have an experimental set-up capable both of reaching very close to the SQL and of showing the onset of different kinds of obscuring noise away from that SQL.”

    This research was supported by the Air Force Office of Scientific Research and the National Science Foundation.

    See the full article here.

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

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  • richardmitnick 8:43 pm on June 17, 2014 Permalink | Reply
    Tags: , , , , , Photon Sciences   

    From Berkeley Lab: “Dynamic Spectroscopy Duo” 

    Berkeley Logo

    Berkeley Lab

    June 17, 2014
    Lynn Yarris

    From allowing our eyes to see, to enabling green plants to harvest energy from the sun, photochemical reactions – reactions triggered by light – are both ubiquitous and critical to nature. Photochemical reactions also play essential roles in high technology, from the creation of new nanomaterials to the development of more efficient solar energy systems. Using photochemical reactions to our best advantage requires a deep understanding of the interplay between the electrons and atomic nuclei within a molecular system after that system has been excited by light. A major advance towards acquiring this knowledge has been reported by a team of researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley.

    Graham Fleming, UC Berkeley’s Vice Chancellor for Research and a faculty senior scientist with Berkeley Lab’s Physical Biosciences Division, led the development of a new experimental technique called two-dimensional electronic-vibrational spectroscopy (2D-EV) . By combining the advantages of two well-established spectroscopy technologies – 2D-electronic and 2D-infrared – this technique is the first that can be used to simultaneously monitor electronic and molecular dynamics on a femtosecond (millionth of a billionth of a second) time-scale. The results show how the coupling of electronic states and nuclear vibrations affect the outcome of photochemical reactions.

    “We think that 2D-EV, by providing unprecedented details about photochemical reaction dynamics, has the potential to answer many currently inaccessible questions about photochemical and photobiological systems,” says Fleming, a physical chemist and internationally acclaimed leader in spectroscopic studies of events that take place on the femtosecond time-scale. “We anticipate its adoption by leading laboratories across the globe,”

    three
    From left, Nicholas Lewis, Graham Fleming and Tom Oliver developed 2D-EV, a spectroscopy technique that enables electronic and molecular dynamics during a photochemical reaction to be simultaneously monitored on a femtosecond time-scale. (Photo by Roy Kaltschmidt)

    [Graham] Fleming is the corresponding author of a paper in the Proceedings of the National Academy of Sciences (PNAS) titled Correlating the motion of electrons and nuclei with two-dimensional electronic–vibrational spectroscopy. Co-authors are Thomas Oliver and Nicholas Lewis, both members of Fleming’s research group.

    Fleming and his research group were one of the key developers of 2D electronic spectroscopy (2D-ES), which enables scientists to follow the flow of light-induced excitation energy through molecular systems with femtosecond temporal resolution. Since its introduction in 2007, 2D-ES has become an essential tool for investigating the electronic relaxation and energy transfer dynamics of molecules, molecular systems and nanomaterials following photoexcitation. 2D infrared spectroscopy is the go-to tool for studying nuclear vibrational couplings and ground-state structures of chemical and complex biological systems.

    “Combining these two techniques into 2D-EV tells us how photoexcitation affects the coupling of electronic and vibrational degrees of freedom,” says Oliver. “This coupling is essential to understanding how all molecules, molecular systems and nanomaterials function.”

    In 2D-EV, a sample is sequentially flashed with three femtosecond pulses of laser light. The first two pulses are visible light that create excited electronic states in the sample. The third pulse is mid-infrared light that probes the vibrational quantum state of the excited system. This unique combination of visible excitation and mid-infrared probe pulses enables researchers to correlate the initial electronic absorption of light with the subsequent evolution of nuclear vibrations.

    “2D-EV’s ability to correlate the initial excitation of the electronic–vibrational manifold with the subsequent evolution of high-frequency vibrational modes, which until now have not been explored, opens many potential avenues of fruitful study, especially in systems where electronic–vibrational coupling is important to the functionality of a system,” Fleming says.

    plants
    Photochemical reactions during photosynthesis enable plants to convert solar energy into chemical energy that is stored as sugars in the plants’ biomass. (Photo by Roy Kaltschmidt)

    As a demonstration, Oliver, Lewis and Fleming used their 2D-EV spectroscopy technique to study the excited-state relaxation dynamics of DCM dye dissolved in a deuterated solvent. DCM is considered a model “push-pull” emitter – meaning it contains both electron donor and acceptor groups – but with a long-standing question as to how it fluoresces back to the ground energy state.

    “From 2D-EV spectra, we elucidate a ballistic mechanism on the excited state potential energy surface whereby molecules are almost instantaneously projected uphill in energy toward a transition state between locally excited and charge-transfer states before emission,” Oliver says. “The underlying electronic dynamics, which occur on the hundreds of femtoseconds time-scale, drive the far slower ensuing nuclear motions on the excited state potential surface, and serve as an excellent illustration for the unprecedented detail that 2D-EV will afford to photochemical reaction dynamics.”

    One example of how 2D-EV might be applied is in the study of rhodopsin, the pigment protein in the retina of the eye that is the primary light detector for vision, and carotenoids, the family of pigment proteins, such as chlorophyll, found in green plants and certain bacteria that absorb light for photosynthesis.

    panels
    Photochemical reactions enable solar panels to convert the energy in sunlight into electrical energy.

    “The nonradiative energy transfer in rhodopsin and carotenoids is thought to involve the breakdown of one of the most widely used approximations of quantum mechanics, the Born-Oppenheimer approximation, which states that since motion of electrons are far faster than nuclei, as represented by vibrational motion, the nuclei respond to changes in electronic states,” Oliver says. “With 2D-EV, we will be able to directly correlate the degrees of electronic and vibrational freedom and track their evolution as a function of time. It’s a chicken and egg kind of problem: Do the electrons or nuclei move first? 2D-EV will give us insight into whether or not the Born-Oppenheimer approximation is still valid in these cases.”

    For nanomaterials, 2D-EV should be able to shed much needed light on how the coupling of phonons – atomic soundwaves – with electrons impacts the properties of carbon nanotubes and other nanosystems. 2D-EV can also be used to investigate the barriers to electron transfer between donor and acceptor states in photovoltaic systems.

    “We are continuing to refine the 2D-EV technology and make it more widely applicable so that it can be used to study lower frequency motions that are of great scientific interest,” Oliver says.

    This research was funded by the DOE Office of Science and the National Science Foundation.

    See the full article here.

    A U.S. Department of Energy National Laboratory Operated by the University of California

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