0000000000075735
AUTHOR
Daniel Peláez
Multiconfigurational second-order perturbation study of the decomposition of the radical anion of nitromethane
The doublet potential energy surfaces involved in the decomposition of the nitromethane radical anion (CH(3)NO(2) (-)) have been studied by using the multistate extension of the multiconfigurational second-order perturbation method (MS-CASPT2) in conjunction with large atomic natural orbital-type basis sets. A very low energy barrier is found for the decomposition reaction: CH(3)NO(2) (-)--[CH(3)NO(2)](-)--CH(3)+NO(2) (-). No evidence has been obtained on the existence of an isomerization channel leading to the initial formation of the methylnitrite anion (CH(3)ONO(-)) which, in a subsequent reaction, would yield nitric oxide (NO). In contrast, it is suggested that NO is formed through the …
Unified model for the ultrafast decay of pyrimidine nucleobases.
Ultrafast decay processes detected after absorption of UV radiation in gas-phase pyrimidine nucleobases uracil, thymine, and cytosine are ascribed to the barrierless character of the pathway along the low-lying 1(pipi*) hypersurface connecting the Franck-Condon region with an out-of-plane distorted ethene-like conical intersection with the ground state. Longer lifetime decays and low quantum yield emission are on the other hand related to the presence of a 1(pipi*) state planar minimum on the S1 surface and the barriers to access other conical intersections. A unified model for the three systems is established on the basis of accurate multiconfigurational CASPT2 calculations, whereas the ef…