Speaker
Description
Light induced charge transfer in molecular complexes containing electron donor and acceptor groups is at the basis of organic photovoltaic devices. To capture the time evolution of this process at the early stages, ideally attosecond time-resolution is required. With the help of elaborate theoretical methods, attosecond pump-probe experiments allow one to image the motion of the “fast” electronic motion in these molecules, mostly in the gas phase, and understand how this motion affects the “slower” motion of atomic nuclei and vice versa. Currently, attosecond pulses produced by high harmonic generation inevitably lead to ionization, so that most of the reported studies concern electron dynamics generated in molecular cations [1-7]. But very recently, UV pulses of few-fs duration have become available [8,9], which combined with attosecond probe pulses, have opened the way to investigations of charge transfer dynamics in neutral molecules with attosecond resolution.
In this talk, I will present the results of theoretical simulations of attosecond pump-probe experiments to investigate the early stages of charge transfer in the donor-acceptor para-nitroaniline (PNA) and meta-nitroaniline (MNA) molecules, both in the neutral and cationic forms. The theoretical approach describes (i) the coherent excitation or ionization of the molecules by the pump pulse, (ii) the ensuing coupled electron and nuclear dynamics, and, in some cases, (iii) the time-resolved photoelectron spectra that should ideally be measured. The results show the strong interdependence between electronic and nuclear motions even during the first few femtoseconds of the charge dynamics.
[1] G. Sansone at al, Nature 465 763 (2010).
[2] F. Calegari et al, Science 346, 336 (2014).
[3] M. Nisoli, P. Decleva, F. Callegari, A. Palacios, and F. Martín, Chem. Rev. 117, 10760 (2017).
[4] F. Calegari and F. Martín, Commun. Chem. 6, 184 (2023).
[5] A. Palacios and F. Martín, WIREs Comput. Mol. Sci. e1430 (2020).
[6] G. Grell et al, Phys. Rev. Res. 5, 023092 (2023).
[7] F. Vismarra et al, Nature Chemistry 16, 2017 (2024).
[8] M. Galli et al, Optics Letters 44, 1308 (2019).
[9] M. Reduzzi et al, Optics Express 31, 26854 (2023).
