From Swiss Federal Institute of Technology in Lausanne [EPFL-École Polytechnique Fédérale de Lausanne] (CH): “Extending the power of attosecond spectroscopy”

From Swiss Federal Institute of Technology in Lausanne [EPFL-École Polytechnique Fédérale de Lausanne] (CH)

01.10.21
Nik Papageorgiou

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Scientists at EPFL have shown that the powerful transient absorption spectroscopy technique can unravel ultrafast motion of electrons and nuclei in a molecule in real time and with atomic spatial resolution.

The last few decades have seen impressive progress in laser-based technologies, which have led to significant advancements in atomic and molecular physics. The development of ultrashort laser pulses now allows scientists to study extremely fast phenomena, like charge transport in molecules and elementary steps of chemical reactions. But beyond that, our ability to observe such processes on the attosecond scale (one quintillionth of a second) means that it is also possible to steer and probe the dynamics of individual electrons on their natural timeframes.

One of the emerging ultrafast technologies is attosecond transient absorption spectroscopy (ATAS), which can track the movement of electrons at a specific site of a molecule. This is a particularly appealing feature of ATAS, because it permits tracing the evolution of the molecular system with spatial resolution at the atomic scale.

Modern lasers can push chemistry into unexplored domains of light-matter interactions, where the role of theory in interpreting the results of ATAS measurements will be more important than ever before. But so far, the theory behind ATAS has been developed only for atoms or for molecules either in the absence of nuclear motion or in the absence of electronic coherence.

Now, a team of physicists from EPFL’s Laboratory of Theoretical Physical Chemistry (LCPT) have extended ATAS theory to molecules, including a full account of the correlated electron-nuclear dynamics.

The work, in collaboration with Alexander Kuleff at Ruprecht Karl University of Heidelberg [Ruprecht-Karls-Universität Heidelberg](DE), is published in Physical Review Letters.

“We present a simple quasi-analytical expression for the absorption cross-section of molecules, which accounts for the nuclear motion and non-adiabatic dynamics and is composed from physically intuitive terms,” says Nikolay Golubev, a postdoc at LCPT and the study’s lead author.

By extending ATAS theory, the scientists also show that this spectroscopy technique has sufficient resolution to “see” the follow-up decoherence of electron motion caused by the molecule’s nuclear rearrangement.

Putting theory into practice, the team tested the polyatomic molecule propiolic acid as an example. “The simulation of X-ray ATAS of the propiolic acid was made possible by combining high-level ab initio electronic structure methods with efficient semiclassical nuclear dynamics,” says Jiří Vaníček, head of the LCPT. By advancing our knowledge of the correlated motion of electrons and nuclei in molecules, the findings of the LCPT researchers could also help our understanding of various other “attochemistry” phenomena.

See the full article here .

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The Swiss Federal Institute of Technology in Lausanne [EPFL-École polytechnique fédérale de Lausanne] (CH) is a research institute and university in Lausanne, Switzerland, that specializes in natural sciences and engineering. It is one of the two Swiss Federal Institutes of Technology, and it has three main missions: education, research and technology transfer.

The QS World University Rankings ranks EPFL(CH) 14th in the world across all fields in their 2020/2021 ranking, whereas Times Higher Education World University Rankings ranks EPFL(CH) as the world’s 19th best school for Engineering and Technology in 2020.

EPFL(CH) is located in the French-speaking part of Switzerland; the sister institution in the German-speaking part of Switzerland is the Swiss Federal Institute of Technology ETH Zürich [Eidgenössische Technische Hochschule Zürich)](CH) . Associated with several specialized research institutes, the two universities form the Domain of the Swiss Federal Institutes of Technology (ETH Domain) [ETH-Bereich; Domaine des Écoles polytechniques fédérales] (CH) which is directly dependent on the Federal Department of Economic Affairs, Education and Research. In connection with research and teaching activities, EPFL(CH) operates a nuclear reactor CROCUS; a Tokamak Fusion reactor; a Blue Gene/Q Supercomputer; and P3 bio-hazard facilities.

ETH Zürich, EPFL (Swiss Federal Institute of Technology in Lausanne) [École polytechnique fédérale de Lausanne](CH), and four associated research institutes form the Domain of the Swiss Federal Institutes of Technology (ETH Domain) [ETH-Bereich; Domaine des Écoles polytechniques fédérales] (CH) with the aim of collaborating on scientific projects.

The roots of modern-day EPFL(CH) can be traced back to the foundation of a private school under the name École spéciale de Lausanne in 1853 at the initiative of Lois Rivier, a graduate of the École Centrale Paris (FR) and John Gay the then professor and rector of the Académie de Lausanne. At its inception it had only 11 students and the offices was located at Rue du Valentin in Lausanne. In 1869, it became the technical department of the public Académie de Lausanne. When the Académie was reorganised and acquired the status of a university in 1890, the technical faculty changed its name to École d’ingénieurs de l’Université de Lausanne. In 1946, it was renamed the École polytechnique de l’Université de Lausanne (EPUL). In 1969, the EPUL was separated from the rest of the University of Lausanne and became a federal institute under its current name. EPFL(CH), like ETH Zürich(CH), is thus directly controlled by the Swiss federal government. In contrast, all other universities in Switzerland are controlled by their respective cantonal governments. Following the nomination of Patrick Aebischer as president in 2000, EPFL(CH) has started to develop into the field of life sciences. It absorbed the Swiss Institute for Experimental Cancer Research (ISREC) in 2008.

In 1946, there were 360 students. In 1969, EPFL(CH) had 1,400 students and 55 professors. In the past two decades the university has grown rapidly and as of 2012 roughly 14,000 people study or work on campus, about 9,300 of these being Bachelor, Master or PhD students. The environment at modern day EPFL(CH) is highly international with the school attracting students and researchers from all over the world. More than 125 countries are represented on the campus and the university has two official languages, French and English.

Organization

EPFL is organised into eight schools, themselves formed of institutes that group research units (laboratories or chairs) around common themes:

School of Basic Sciences (SB, Jan S. Hesthaven)

Institute of Mathematics (MATH, Victor Panaretos)
Institute of Chemical Sciences and Engineering (ISIC, Emsley Lyndon)
Institute of Physics (IPHYS, Harald Brune)
European Centre of Atomic and Molecular Computations (CECAM, Ignacio Pagonabarraga Mora)
Bernoulli Center (CIB, Nicolas Monod)
Biomedical Imaging Research Center (CIBM, Rolf Gruetter)
Interdisciplinary Center for Electron Microscopy (CIME, Cécile Hébert)
Max Planck-EPFL Centre for Molecular Nanosciences and Technology (CMNT, Thomas Rizzo)
Swiss Plasma Center (SPC, Ambrogio Fasoli)
Laboratory of Astrophysics (LASTRO, Jean-Paul Kneib)

School of Engineering (STI, Ali Sayed)

Institute of Electrical Engineering (IEL, Giovanni De Micheli)
Institute of Mechanical Engineering (IGM, Thomas Gmür)
Institute of Materials (IMX, Michaud Véronique)
Institute of Microengineering (IMT, Olivier Martin)
Institute of Bioengineering (IBI, Matthias Lütolf)

School of Architecture, Civil and Environmental Engineering (ENAC, Claudia R. Binder)

Institute of Architecture (IA, Luca Ortelli)
Civil Engineering Institute (IIC, Eugen Brühwiler)
Institute of Urban and Regional Sciences (INTER, Philippe Thalmann)
Environmental Engineering Institute (IIE, David Andrew Barry)

School of Computer and Communication Sciences (IC, James Larus)

Algorithms & Theoretical Computer Science
Artificial Intelligence & Machine Learning
Computational Biology
Computer Architecture & Integrated Systems
Data Management & Information Retrieval
Graphics & Vision
Human-Computer Interaction
Information & Communication Theory
Networking
Programming Languages & Formal Methods
Security & Cryptography
Signal & Image Processing
Systems

School of Life Sciences (SV, Gisou van der Goot)

Bachelor-Master Teaching Section in Life Sciences and Technologies (SSV)
Brain Mind Institute (BMI, Carmen Sandi)
Institute of Bioengineering (IBI, Melody Swartz)
Swiss Institute for Experimental Cancer Research (ISREC, Douglas Hanahan)
Global Health Institute (GHI, Bruno Lemaitre)
Ten Technology Platforms & Core Facilities (PTECH)
Center for Phenogenomics (CPG)
NCCR Synaptic Bases of Mental Diseases (NCCR-SYNAPSY)

College of Management of Technology (CDM)

Swiss Finance Institute at EPFL (CDM-SFI, Damir Filipovic)
Section of Management of Technology and Entrepreneurship (CDM-PMTE, Daniel Kuhn)
Institute of Technology and Public Policy (CDM-ITPP, Matthias Finger)
Institute of Management of Technology and Entrepreneurship (CDM-MTEI, Ralf Seifert)
Section of Financial Engineering (CDM-IF, Julien Hugonnier)

College of Humanities (CDH, Thomas David)

Human and social sciences teaching program (CDH-SHS, Thomas David)

EPFL Middle East (EME, Dr. Franco Vigliotti)[62]

Section of Energy Management and Sustainability (MES, Prof. Maher Kayal)

In addition to the eight schools there are seven closely related institutions

Swiss Cancer Centre
Center for Biomedical Imaging (CIBM)
Centre for Advanced Modelling Science (CADMOS)
École cantonale d’art de Lausanne (ECAL)
Campus Biotech
Wyss Center for Bio- and Neuro-engineering
Swiss National Supercomputing Centre