Jan 13 – 15, 2021
Paul Scherrer Institut
Europe/Zurich timezone

Time-Dependent Quantum Model for Attosecond X-ray Non-Linear Spectroscopy

Jan 13, 2021, 6:40 PM
20m
Virtual only (Paul Scherrer Institut)

Virtual only

Paul Scherrer Institut

Forschungsstr. 111 CH-5232 Villigen
WavemiX 2021

Speaker

Dr Solène Oberli (Ecole Polytechnique Fédérale de Lausanne)

Description

The recent capacity of X-ray free-electron lasers (XFELs) to produce ultrashort and intense X-ray pulses gives access to the observation of electron motion in molecules with high temporal (attosecond) and spatial (angström) resolutions. In the present study, we use a promising nonlinear technique called impulsive stimulated X-ray Raman scattering (ISXRS) to produce a coherent superposition of neutral excited electronic states in nitric oxide (NO) [1]. An attosecond X-ray pulse first core-excites the O atom, promoting a core electron to a 2π* orbital. Before this short-lived core-excited state decays, a second photon is absorbed from the same X-ray pulse and creates a coherent superposition of neutral valence-excited states. A time-delayed femtosecond UV pulse probes the induced dynamics by ionizing the molecule, and the NO+ yield allows us to quantify the population transfer induced by the ISXRS process.
We developed a sophisticated quantum model to interpret this first experimental demonstration of ISXRS in a molecule. It is based on the time-dependent Schrödinger equation for the electrons, and takes into account the interaction of the X-ray pulse with the molecule, the Auger decay, as well as the strong electron correlation effects in the presence of a core vacancy. With this model, we are able to provide a quantitative and qualitative interpretation of the ISXRS process, as well as to characterize the X-ray pulse parameters. This work
demonstrates the possibility to induce electronic population transfer via ISXRS using a single attosecond X-ray pulse, and sheds light on the role of electronic coherences at the earliest stage of chemical processes. Moreover, this study is relevant for future two color attosecond X-ray pump / X-ray probe set-ups that will also permit to probe site-selectively the induced dynamics at a remote atom in the molecule. This joint experimental and theoretical investigation is thus a stepping stone towards studying electronic dynamics in more complex systems and opens a path for investigation of transient electronic phenomena in matter at XFEL facilities.

[1] J. T. O'Neal et al., Phys. Rev. Lett., 125 073203 (2020)

Primary authors

Dr Solène Oberli (Ecole Polytechnique Fédérale de Lausanne) Prof. Antonio Picón (Departamento de Química, Universidad Autónoma de Madrid, Madrid 28049, Spain) Mr Jordan T. O'Neal (Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA and Department of Physics, Stanford University, Stanford, California 94305, USA) Mr Elio G. Champenois (Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA) Dr Andre Al-Haddad (Paul-Scherrer Institute, CH-5232, Villigen PSI, Switzerland and Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA) Prof. Agostino Marinelli (Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA) Prof. James P. Cryan (Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA and Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA)

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