Nonradiative decay (NRD) processes such as internal conversion (IC) and intersystem crossing (ISC) govern photo-functionality of living systems such as the photostability of the DNA, phototaxis, visual perception etc. Understanding this complex NRD pathways of biomolecules should help us develop bio-inspired photo-functional materials. In this talk, we will share our recent theoretical works on the multistep NRD pathways of biomolecules in gas phase with the aids of pump-probe experiments:

(1) Structure dependent photoisomerization routes of cinnamate based sunscreens^1,2

We found that the structural isomers of cinnamate based sunscreens undergo trans → cis photo-isomerization under UV irradiation but differ in the isomerization pathway (ISC or IC) ^1,2. These results suggest that controlling the substitution position is essential to design the cinnamate based photo-functional materials.

(2) Ultrafast nonadiabatic cascade of XUV excited caffeine molecule³

We also found the XUV excited caffeine molecule undergoes a nonadiabatic cascade via ~100 highly correlated mono-cationic states. These results show that both nonadiabatic coupling and electron correlation are the keys for ultrafast reaction dynamics in the highly-correlated electronic excited states.

References:
[1] K. Yamazaki, S. Maeda*, M. Ehara*, T. Ebata* et al., J. Phys. Chem. Lett. 7, 4001 (2016).
[2] S. Kinoshita, K. Yamazaki*, M. Ehara*, T. Ebata* et al., Phys. Chem. Chem. Phys. 20, 17583 (2018).
[3] A. Marciniak, K. Yamazaki*, F. Lépine* et al., J. Phys. Chem. Lett., submitted (2018).
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