Ab initio quantum dynamical study of the vinylidene-acetylene isomerization

The dynamics of vinylidene-acetylene isomerization has been studied quantum mechanically, based on a new ab initio calculated potential energy surface (PES). The grid underlying the PES and the dynamic treatment rest on plana r 4-atom Jacobi-like coordinates. Three degrees of freedom, the C-C bond le ngth and the two Jacobi-like angles are treated explicitly, while the two o ther coordinates relating to the C-H bond lengths have been optimized in th e ab initio trealment. The energies of the resulting 3D grid have been comp uted with the CCSD(T) method, using a cc-pVTZ basis set, while selected sta tionary points have been characterized at a higher level of theory. The sub sequent dynamic treatment reproduces very satisfactorily the experimental p hotodetachment spectrum of Lineberger and coworkers. Preliminary results ar e also reported for the lifetime of vinylidene.