We aim at measuring ultrafast processes in atoms, molecules, and solids using innovative spectroscopic techniques based on high-order harmonics, strong-field driven attosecond electron wavepackets, XUV photoemission spectroscopy, as well as fs-REMPI (resonant enhanced multiphoton ionization) using to velocity map imaging, COLTRIMS and ARPES detection schemes. These research interests lead us to develop theoretical tools to describe the main steps of undergoing pump-probe experiments.

The HarMoDyn team is located in the laboratory CEntre Lasers Intenses et Applications (CELIA - CNRS UMR 5107) at Universite de Bordeaux , 351 Cours de la Libération, 33405 TALENCE CEDEX, France.

CELIA facilities are accessible through the national LOA-LIDYL-CELIA call,  and via LASERLAB Europe.

                   https://erc.europa.eu/sites/default/files/LOGO_ERC-FLAG_EU%20NEGATIF.jpg

One of our main research interests is the investigation of ultrafast dynamics of chiral molecules in the gas phase, on the femtosecond and attosecond timescale. This is the goal of the EXCITERS project - Extreme Ultraviolet Circular Time-Resolved Spectroscopy - funded by the European Reseach Council (ERC) under the European Union's Horizon 2020 research and innovation programme. This project aims at developping innovative tools based on high-repetition rate fiber laser systems, coincidence electron-ion imaging and high harmonic spectroscopy, to study chiral molecules. 

 

 

Highlights

Electrons on the run

Will an electron escaping a molecule through a quantum tunnel behave differently depending on the left- or right-handedness of the molecule?

https://phys.org/news/2022-12-electrons-chirality-tunneling-fields.html

Revealing the Influence of Molecular Chirality on Tunnel-Ionization Dynamics, E. Bloch et al. Phys. Rev. X 11, 041056

A new observable in ARPES

We introduced a novel measurement methodology and associated observable in extreme ultraviolet (XUV) angle-resolved photoemission spectroscopy (ARPES), based on continuous modulation of the ionizing radiation polarization axis. Tracking the energy- and momentum-resolved amplitude and phase of the photoemission intensity modulation upon polarization axis rotation allows us to retrieve the circular dichroism in photoelectron angular distributions (CDAD) without using circular photons, providing direct insights into the phase of photoemission matrix elements. 

Polarization-modulated angle-resolved photoemission spectroscopy: Toward circular dichroism without circular photons and Bloch wave-function reconstruction, Michael Schüler, Tommaso Pincelli, Shuo Dong, Thomas P Devereaux, Martin Wolf, Laurenz Rettig, Ralph Ernstorfer, Samuel Beaulieu, Physical Review X 12 (1), 011019 (2022)

 

Photoelectron Elliptical Dichroism Spectroscopy

When chiral molecules are ionized by elliptically polarized laser pulses, a strong forward/backward asymmetry appears in the angular distribution of the photoelectrons. In this recent article published in PCCP, we use this PhotoElectron Elliptical Dichroism (PEELD) as a spectroscopic tool to investigate the influence of different Rydberg states in the resonance-enhanced multiphoton ionization of fenchone by tunable femtosecond pulses.

Physics Focus: Molecular Probe Uses a Polarization Flip

Read an article on Physics describing our recent results on shaping the sub-cycle optical chirality of a laser field to probe molecular chirality:

Focus: Molecular Probe Uses a Polarization FlipFocus: Molecular Probe Uses a Polarization Flip

The results are published in Physical Review X:

Controlling Subcycle Optical Chirality in the Photoionization of Chiral Molecules,

S. Rozen, A. Comby, E. Bloch, S. Beauvarlet, D. Descamps, B. Fabre, S. Petit, V. Blanchet, B. Pons, N. Dudovich, and Y. Mairesse, Phys. Rev. X 9, 031004 (2019)

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Real-time determination of enantiomeric and isomeric content using photoelectron elliptical dichroism

The fast and accurate analysis of chiral chemical mixtures is crucial for many applications but remains challenging. Here we use elliptically-polarized femtosecond laser pulses at high repetition rates to photoionize chiral molecules. The 3D photoelectron angular distribution produced provides molecular fingerprints, showing a strong forward-backward asymmetry which depends sensitively on the molecular structure and degree of ellipticity. Continuously scanning the laser ellipticity and analyzing the evolution of the rich, multi-dimensional molecular signatures allows us to observe real-time changes in the chemical and chiral content present with unprecedented speed and accuracy. We measure the enantiomeric excess of a compound with an accuracy of 0.4% in 10 min acquisition time, and follow the evolution of a mixture with an accuracy of 5% with a temporal resolution of 3 s. This method is even able to distinguish isomers, which cannot be easily distinguished by mass-spectrometry.

Real-time determination of enantiomeric and isomeric content using photoelectron elliptical dichroism
A. Comby, E. Bloch, C. M. M. Bond, D. Descamps, J. Miles, S. Petit, S. Rozen, J. B. Greenwood, V. Blanchet & Y. Mairesse, Nature Communications 9, 5212 (2018)

PicturePEELDlite