Ab initio quantum dynamical study of photoinduced ring opening in furan

The nonadiabatic photoinduced ring opening occurring in the two lowest excited singlet states of furan is investigated theoretically, using wave-packet propagation techniques. The underlying multidimensional potential energy surfaces (PESs) are obtained from ab initio computations, using the equation-of-motion coupled cluster method restricted to single and double excitations (EOM-CCSD), reported in earlier recent work [ E. V. Gromov , A. B. Trofimov , F. Gatti , and H. Köppel , J. Chem. Phys. 133 , 164309 ( 2010 ) 10.1063/1.3493451 ] . Up to five nuclear degrees of freedom are considered in the quantum dynamical treatment. Four of them represent in-plane motion for which the electronic states in question (correlating with the valence 1 B 2 ( V ) and Rydberg 1 A 2 (3 s ) states at the C 2 v ground-state molecular configuration) have different symmetries, A ′ and A ′′ , respectively. The fifth mode, representing out-of-plane bending of the oxygen atom against the carbon-atom plane, leads to an interaction of these states, as is crucial for the photoreaction. The nonadiabatic coupling and conical intersection cause an electronic population transfer on the order of ∼10 fs. Its main features, and that of the wave-packet motion, are interpreted in terms of properties of the PES. The lifetime due to the ring-opening process has been estimated to be around 2 ps. The dependence of this estimate on the nuclear degrees of freedom retained in the computations is discussed.