Programme

P.85 -- Posters, VCTP-50

Date: Thursday, 7 August 2025

Time: 08:30 - 10:00

PROBING CHARGE MIGRATION OF MOLECULAR ION FROM HIGH-HARMONIC SPECTRA

Thanh-Duy D.Nguyen (1), Doan-An Trieu (2), Thanh Tran (1), Duong D. Hoang-Trong (3), Ngoc-Loan Phan (1)

(1)Computational Physics Key Laboratory K002, Department of Physics, Ho Chi Minh City University of Education, Ho Chi Minh City 72711, Vietnam (2)Institute of Fundamental and Applied Sciences, Duy Tan University, Ho Chi Minh City 700000, Vietnam (3)Simulation in Materials Science Research Group, Science and Technology Advanced Institute, Van Lang University, Ho Chi Minh City, Vietnam

Attosecond physics is a pioneering field that explores ultrafast dynamics at the attosecond timescale, particularly the motion of electrons in atoms and molecules [1]. A phenomenon of interest is charge migration (CM), which refers to the temporal change in electron density within excited molecules [1]. Investigating CM is highly significant for understanding and controlling chemical reactions, offering the potential to enhance reaction efficiency and reveal novel reaction mechanisms [1]. To probe this ultrafast electron dynamic, high-harmonic generation (HHG) spectra emerge as a powerful tool [2-4]. The mechanism of HHG signal emission is described by the semiclassical three-step model, where an electron is ionized, propagates in the laser field, and recombines with the parent ion, emitting an HHG signal [8]. The next recombination takes place after a few attoseconds, emitting another HHG signal [2]. These signals encode image of the ion at the moment of recombination [3]. By analyzing the attosecond-scale HHG signals emitted, we reconstruct the attosecond-resolution “movies” of electron density in molecular ions, enabling direct observation of charge migration [2-4]. While the CM reconstruction method from HHG spectra has been applied to various molecular ion [2-4], their quantitative accuracy remains uncharacterized. In this study, we implement this approach on carbonyl sulfide ion (OCS⁺) - a previously unexplored target for CM studies, in which, the measured HHG spectra are considered as single-molecule response. In our results, we successfully reconstruct the CM of OCS⁺ from HHG spectra and validate the accuracy method against TDDFT simulation. The reconstructed CM shows excellent agreement with theoretical predictions, quantitatively confirming the method’s is under 20% error. The project is ongoing, aiming to probe CM of OCS⁺ from HHG spectra of a gaseous sample of OCS molecule. References: [1] Krausz, F., & Ivanov, M. (2009). Attosecond physics. Reviews of Modern Physics, 81(1), 163. [2] Kraus, P. M., Mignolet, B., Baykusheva, D., Rupenyan, A., Horný, L., Penka, E. F., ... & Wörner, H. J. (2015). Measurement and laser control of attosecond charge migration in ionized iodoacetylene. Science, 350(6262), 790. [3] He, L., Sun, S., Lan, P., He, Y., Wang, B., Wang, P., ... & Lin, C. D. (2022). Filming movies of attosecond charge migration in single molecules with high harmonic spectroscopy. Nature Communications, 13(1), 4595. [4] He, L., He, Y., Sun, S., Goetz, E., Le, A. T., Zhu, X., ... & Lin, C. D. (2023). Attosecond probing and control of charge migration in carbon-chain molecule. Advanced Photonics, 5(5), 056001. [5] Lewenstein, M., Balcou, P., Ivanov, M. Y., L’huillier, A., & Corkum, P. B. (1994). Theory of high-harmonic generation by low-frequency laser fields. Physical Review A, 49(3), 2117.

Presenter: Nguyen Thanh Dinh Duy