Three-dimensional quantum mechanical study of Ne⋅⋅⋅Cl2 vibrational predissociation

Abstract

Three-dimensional quantum mechanical calculations for vibrational predissociation of the Ne⋅⋅⋅Cl2 van der Waals complex are presented and compared with experiments. Lifetimes and final rotational state distributions were obtained for the two processes: (i) Ne⋅⋅⋅Cl2(X,v=1) →Ne+Cl2(X,v=0) and (ii) Ne⋅⋅⋅Cl2(B,v=11) →Ne +Cl2(B,v=10,9) where v denotes the vibrational quantum number of Cl2 and X and B specify electronic states of Ne⋅⋅⋅Cl2 which correlate with the X 1∑+0g and B 3∏+0u states of the free Cl2 molecule, respectively. The van der Waals interaction potential was taken to have the same form in the X and B states. At short distances, it is described by a sum of Morse pairwise potentials between the Ne atom and each of the Cl atoms, and between the neon atom and the center of mass of Cl2. At large distances the potential switches to an anisotropic van der Waals interaction with R−6 and R−8 dependence. The parameters were adjusted so that the T-shaped configuration the potential matched the one determined from scattering experiments. The initial quasibound state wave function of the complex was calculated variationally, while the final continuum wave functions were obtained by integration of the rotational close coupled Schrödinger equations. Finally, the lifetime and the final rotational state distribution were calculated using the Fermi golden rule. A line shape calculation verified the validity of the golden rule approximation for this system. The lifetimes obtained for the X and the B states differ by several orders of magnitude, the X state being the longest lived as observed experimentally. The calculated lifetimes and rotational distributions of the Cl2 fragments agree qualitatively with the experimental values. The rotational distribution is compared to that obtained from a decomposition of the initial quasibound state in terms of free rotor states.