Regular vibrational state progressions at the dissociation limit of SCCl₂

We observe sharp features in the vibrational spectrum of SCCl₂ at and above its two lowest-lying dissociation limits. Highly regular vibrational progressions persist at dissociation, as in some smaller molecules studied previously by others. Nearly all of the SCCl₂ transitions studied by stimulated emission pumping can be assigned and fitted by a simple effective Hamiltonian without resonance terms, up to a total vibrational excitation of 36 quanta. The character of the highly excited vibrational wave functions is not normal mode-like, but it nonetheless arises gradually from the normal modes as the energy increases. The number of sharp vibrational features observed matches a scaling model that predicts localization of nearly all vibrational states near dissociation as the size of a polyatomic molecule increases.