Quantum-classical effective-modes dynamics of the $π$$π$ * → n$π$* decay in 9H-adenine. A quadratic vibronic coupling model

TitleQuantum-classical effective-modes dynamics of the $π$$π$ * → n$π$* decay in 9H-adenine. A quadratic vibronic coupling model
Publication TypeJournal Article
Year of Publication2013
AuthorsPicconi, D, Avila, F, Improta, R, Lami, A, Santoro, F
JournalFaraday Discussions
Volume163
Pagination223–242
ISSN13596640 (ISSN)
KeywordsAdenine, Article, Chemical, chemical model, chemistry, Models, molecular dynamics, molecular dynamics simulation
Abstract

We present mixed quantum-classical simulation of the internal conversion between the lowest energy $π$$π$* (SLa) and n$π$* (Sn) excited electronic states in adenine in the gas phase, adopting a quadratic vibronic model (QVC), parametrized with the help of PBE0 density functional calculations. Our approach is based on a hierarchical representation of the QVC Hamiltonian and a subsequent treatment of the most relevant coordinates at accurate time-dependent quantum level and of the other 'bath' modes at classical level. We predict an ultrafast transfer (∼30 fs) of ≈75% of the initial population excited on SLa to Sn. Within an adiabatic picture, on the same timescale the wave packet concentrates almost completely on the lowest S1 state, where however it shows a very broad distribution with different characteristics (due to the different 'diabatic' character). It is shown that the proposed methodology offers a practicable route to describe the quantum dynamics of internal conversion processes in large semi-rigid systems. © 2013 The Royal Society of Chemistry.

URLhttp://xlink.rsc.org/?DOI=c3fd20147c http://www.scopus.com/inward/record.url?eid=2-s2.0-84881110392&partnerID=40&md5=2e9d2340e611a739851d8b209eba73e7
DOI10.1039/c3fd20147c