THEORETICAL STUDY OF THE SPECTROSCOPY AND DYNAMICS OF THE VINYLIDENE-ACETYLENE ISOMERIZATION

$^{a}$R. Schork, and H. K\""{o}ppel, Theor. Chem. Acc. 100, 204 (1998). $^{b}$K. M. Ervin, J. Ho, and W. C. Lineberger, J. Chem. Phys. 91, 5974 (1989).Author Institution: Theoretical Chemistry, University of HeidelbergThe results of 5D ab initio quantum dynamical study of the vinylidene - acetylene isomerization reaction are presented. The study is based on a new ab initio potential energy surface for the planar system, obtained with the CCSD(T) method and the cc-pVTZ basis set. The dynamics is studied with grid methods, using 4-atom Jacobi-like coordinates and wave packet propagation techniques. The results of a 3D treatment, including the 2 angular degrees of freedom and the C-C stretching mode, have been reported earlier in the $literature^{a}$. Including all (planar) degrees of freedom, the experimental photodetachment spectrum of Lineberger and $coworkers^{b}$ is very well reproduced. Furthermore, lifetimes for broadband excitation and for individual vibrational levels of vinylidene have been computed, the latter with the aid of filter diagonalization techniques. The lifetimes are 2-3 orders of magnitude longer that previously believed, indicating a surprising stability of this reactive intermediate. Similar results have been obtained for the deuterated species, $D_{2}CC$ supporting the above conclusions