Browsing by Author "Mignolet, Benoit"

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Ultrafast nonradiative transition pathways in photo-excited pyrazine: Ab initio analysis of time-resolved vacuum ultraviolet photoelectron spectrum
(2018-11-14)
Mignolet, Benoit
;
Kanno, Manabu
;
Shimakura, Noriyuki
;
Koseki, Shiro
;
Remacle, Francoise
The internal conversion of photo-excited pyrazine, which occurs rapidly on a time scale of about 20 fs, has long been considered to proceed via a conical intersection between the optically bright S-2 (B-1(2u), pi pi*) and dark S-1 (B-1(3u), n pi*) states. Since 2008, several theoretical studies have raised the possibility that other dark states S-3 ((1)A(u), n pi*) and S-4 (B-1(2g), n pi*) may participate dominantly in the early stage of the nonradiative decay of S-2. To clarify this issue, being motivated by the recent pump-probe experiment by Horio et al. [J. Chem. Phys. 145 (2016) 044306], we calculated vacuum ultraviolet photoelectron spectra for ionization from each of the four excited states. Comparison was made with the measured time-resolved photoelectron spectrum exhibiting a temporally varying multi-band structure. We confirmed no contribution of S-3 or S-4 and thus the validity of the conventional two-state (S-2 -> S-1) picture for ultrafast nonradiative transition in pyrazine.