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Are Conical Intersections Responsible for the Ultrafast Processes of Adenine, Protonated Adenine, and the Corresponding Nucleosides?
Author(s) -
Brøndsted Nielsen Steen,
Sølling Theis I.
Publication year - 2005
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.200400644
Subject(s) - chemistry , conical intersection , photoexcitation , protonation , photodissociation , ground state , potential energy surface , excited state , potential energy , density functional theory , molecule , internal conversion , photochemistry , computational chemistry , atomic physics , quantum mechanics , physics , ion , organic chemistry , spectral line
Abstract Excited‐state potential energy surfaces of adenine, protonated adenine, and their N9‐methylated analogs are explored by means of a complete active space (CAS) and time‐dependent density functional theory (TD‐DFT) study to understand the dynamics associated with internal conversion. After photoexcitation of the ground‐state molecules to the S 1 state, the nuclear motions that are responsible for taking the wavepacket out of the Franck–Condon region are either an HN9/CN9 stretch or a ring‐puckering motion that leads to pyramidalization. These motions lead to accessible conical intersections with the ground‐state surface. The results are used to successfully interpret previous measurements on the photodissociation of adenosine 5′‐monophosphate nucleotide anions and cations, where the latter react in a highly nonstatistical manner.