Programme

O.10 -- Oral, VCTP-48

Date: Tuesday, 1 August 2023

Time: 15:05 - 15:30

Real-time monitoring molecular dynamics using high-order harmonic generation

Doan-An Trieu, Ngoc-Loan Phan, Van-Hoang Le

Computational Physics Laboratory K002, Department of Physics, Ho Chi Minh City University of Education, Ho Chi Minh City 72711, Vietnam

Chemical reactions are the result of the coupled dynamics of electrons and nuclei in molecules. Hence, finding methods for monitoring molecular dynamics are required for a comprehensive understanding of chemical reactions [1]. Being pioneered by Zewail, the pump-probe scheme using ultrashort laser pulses has become popular and successful in monitoring molecular nuclear vibration, dissociation, isomerism, and so on [2]. This scheme proposes using a ``pump" pulse to excite dynamical processes and a ``probe" pulse to generate emission of molecular spectra. By measuring a specific spectrum versus time delay between the pump and probe pulses, molecular dynamics can be extracted from the spectral properties. In practice, mass spectroscopy, Coulomb explosion, photoelectron spectroscopy, high-order harmonic generation (HHG) are different kinds of spectrum for studying molecular dynamics [2,3]. However, HHG, the laser-induced generation of high-frequency photons, is rarely applied, in spite of its high spatiotemporal resolution. Therefore, in our current project, we aim to use HHG to probe molecular dynamics, particularly the dissociation. Until now, we have been successful in constructing a procedure for simulating HHG in a dissociative process of hydrogen ion. According to this procedure, we first calculate the molecular adiabatic potential energy surfaces (PES); then, we simulate the molecular dynamics, including laser-induced excitation and nuclear wavepacket evolution on the PES; finally, we calculate the time-delayed HHG by coherently adding HHG from all molecular adiabatic states. Currently, the procedure is being modified for methyl iodide, whose monitoring dynamics process is more challenging due to the presence of the conical intersection between two dissociative surfaces - a critical problem in molecular dynamics [4]. In this report, our newest results will be shown in detail. [1] T. R. Nelson et al., ”Non-adiabatic Excited-State Molecular Dynamics: Theory and Applications for Modeling Photophysics in Extended Molecular Materials,” Chemical Reviews 120, 2215 (2020). 2] A. H. Zewail, ”Femtochemistry: Atomic-scale dynamics of the chemical bond,” Journal of Physical Chemistry A 104, 5660 (2000). [3] Peter M. Kraus et al., ”The ultrafast X-ray spectroscopic revolation in chemical dynamics,” Nature Reviews Chemistry 2, 82 (2018). [4] Maria E. Corrales et al., ”Coulomb Explosion Imaging for the Visualization of a Conical Intersection,” Journal of Physical Chemistry Letters 10, 138 (2019).

Presenter: Trieu Doan-An