Hybrid quantum/classical study of ICN in an Ar matrix: Photofragmentation and cage exit

The (A) over tilde continuum photoexcitation of ICN in an Ar matrix is studied using an implementation of the molecular dynamics with quantum transitions method of Tully. Five excited electronic potential energy surfaces of the ICN molecule, (3)Pi(0+), (1)Pi(1)(A',A "), (3)Pi(1)(A',A "), as well as its ground state, are included in these calculations. The couplings between electronic states at large I-CN internuclear distances are modeled using a diatomic in molecules treatment of the mixing of the different spin-orbit states of iodine induced by the Ar atoms. The electronic motion, as well as the I-CN distance and the corresponding bending angle, are treated quantum mechanically using wave-packet techniques. The rotation and translation of the ICN molecule in the Ar cage are treated classically, as well as the motion of the Ar atoms. In contrast with previous calculations, in which all nuclear degrees of freedom were treated classically, we found a 2% of CN cage exit during the first 0.5 ps of the dynamics. (C) 2000 American Institute of Physics. [S0021-9606(00)00427-X].