Ultrafast non-adiabatic relaxation in XUV-excited molecules: Dynamics in correlation bands

Exposing molecules to XUV radiation typically populates highly excited cationic states, triggering complex ultrafast dynamics where electronic and nuclear motions are strongly coupled. A fully quantum description of these dynamics in small polycyclic aromatic hydrocarbons (PAHs) will be presented and compared to time-resolved experimental results [1-3]. It will be shown that non-adiabatic relaxation dynamics slows down as the initial excitation approaches the double-ionization threshold and as the molecular size increases. Furthermore, the dynamics in this energy range are governed by the so-called correlation bands--regions of high density-of-states arising from strong electron correlation in the inner valence. A simple electron-phonon scattering model is shown to effectively explain and predict the relaxation timescales across entire classes of molecules [4]. Additionally, it will be demonstrated that ultrafast correlation-driven charge migration, which occurs immediately after the removal of an inner-valence electron and the population of the correlation band, typically leads to a redistribution of hole charge within the molecule, enhancing the system's stability [5].
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[1] A. Marciniak, et al., Nature Commun. 6, 7909 (2015).
[2] A. Marciniak, et al., Nature Commun. 10, 337 (2019).
[3] A. Boyer, et al., Phys. Rev. X 11, 041012 (2021)
[4] M. Hervé, et al., Nature Phys. 17, 327 (2021).
[5] V. Despré and A. I. Kuleff, Phys. Rev. A 106, L021501 (2022).