Theoretical Study toward Understanding Ultrafast Internal Conversion of Excited 9H-Adenine
- 31 August 2005
- journal article
- Published by American Chemical Society (ACS) in The Journal of Physical Chemistry A
- Vol. 109 (38) , 8443-8446
- https://doi.org/10.1021/jp0537207
Abstract
The CASPT2/CASSCF method with the 6-311G basis set and an active space up to (14, 11) was used to explore the ultrafast internal conversion mechanism for excited 9H-adenine. Three minima, two transition states, and seven conical intersections were obtained to build up the two deactivation pathways for the internal conversion mechanism. Special efforts were made to explore the excited-state potential energy surfaces near the Franck-Condon region and determine the various barriers in the processes of deactivation. The barrier required from the 1pipi (1La) state to deactivate nonradiatively is found to be lower than that required from the 1pipi (1Lb) state. On 250 nm excitation, the 1pipi (1La) state is populated, and the transition from 1pipi (1La) to the lowest 1npi state involves very low barriers, which may account for the observed short (2 ps lifetime.Keywords
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