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Photoinduced Nonadiabatic Dynamics of 9 H ‐Guanine
Author(s) -
Lan Zhenggang,
Fabiano Eduardo,
Thiel Walter
Publication year - 2009
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200900030
Subject(s) - conical intersection , relaxation (psychology) , excited state , surface hopping , internal conversion , chemistry , atomic physics , excitation , atom (system on chip) , intersection (aeronautics) , displacement (psychology) , molecular physics , guanine , physics , spectral line , quantum mechanics , psychology , social psychology , nucleotide , biochemistry , computer science , embedded system , engineering , psychotherapist , gene , aerospace engineering
Surface‐hopping simulations are used to study the nonradiative relaxation of 9 H ‐guanine. Two distinct S 1 →S 0 (ππ*→gs) decay channels, both of which pass through a conical intersection (CI), are found to be responsible for the experimentally observed double‐decay behavior (see schematic diagram).The photoinduced nonadiabatic decay dynamics of 9 H ‐guanine is investigated by surface‐hopping calculations at the semiempirical OM2/MRCI level of theory. Following excitation, fast internal conversion from the ππ* (L a ) excited state to the ground state is observed within 800 fs. Relaxation proceeds through two distinct S 1 →S 0 pathways. The first channel goes through a conical intersection with pronounced out‐of‐plane displacement of the C2 atom and yields ultrafast decay with a time constant of 190 fs. The second channel evolves through a conical intersection with strong out‐of‐plane distortion of the amino group and leads to slower decay with a lifetime of 400 fs. These decay mechanisms and the computed decay times are consistent with the available experimental evidence and previous theoretical studies.