Speaker
Description
Photoinduced electron transfer and charge transfer processes occurring in organic and inorganic materials are the cornerstone of technologies aiming at the conversion of solar energy into electrical energy and at its efficient transport. The early stages of these processes occur in the attosecond time scale, the natural time scale for electronic motion in atoms and molecules. Accessing this time scale requires the use of light pulses with a duration below the femtosecond, which were first produced in the lab at the dawn of this millennium. The first attosecond experiments aiming at the observation of electronic motion in organic molecules date from 2014 [1]. The usual approach in these experiments is to employ an attosecond pulse to generate an electronic wave packet that subsequently evolves under the influence of the nuclear motion and to interrogate the system with a second pulse at a given time delay in order to obtain a picture of the system at that particular time. By varying the delay between the two pulses, one can thus obtain a sequence of frames or the “movie” of the electronic motion.
The experiments usually record photoelectron and/or fragmentation yields as a function of the temporal delay between the two pulses with attosecond resolution. However, in spite of the successful observation of sub- and few-fs dynamics in the recorded yields [1-4], it is not yet clear how the early electron dynamics leaves its signature in molecular fragments that may be created long after those initial steps (usually after going through a series of non adiabatic processes) or why one should expect a reminiscence of such electron dynamics at all. To answer these questions, one must understand i) the electronic excitation or ionization induced by the first pulse, ii) the coupled electron and nuclear dynamics that follows, iii) the interaction of the second pulse with a molecular system in a coherent superposition of states, and iv) the coupled electron and nuclear dynamics that follows the last step and eventually leads to fragmentation of the molecule. Every step is in itself a theoretical and experimental challenge for molecules containing more than two nuclei. In this talk I will review recent experimental and theoretical efforts to account for these four steps and discuss the optimum conditions to visualize electron dynamics in molecules [5].
[1] F. Calegari et al, Science 346, 336 (2014).
[2] M. Nisoli, P. Decleva, F. Callegari, A. Palacios, and F. Martín, Chem. Rev. 117, 10760 (2017).
[3] M. Lara-Astiaso et al, J. Phys. Chem. Lett. 9, 4570 (2018).
[4] J. Delgado et al, Faraday Discussions, 228, 349 (2021).
[5] A. Palacios and F. Martín, WIREs Comput. Mol. Sci. e1430 (2020).
