An effective Hamiltonian survey of the anharmonic vibrational state spaceof SCCl_2up to the dissociation energy

摘要

We survey about 3.5 million feature states in the anharmonic state space of SCCl_2to answer threequestions: how sharp is the threshold for intramolecular vibrational energy redistribution (IVR),how do specific resonances and regions of state space contribute to the threshold, and how manyundiluted spectral features (or localized eigenstates) persist as energy increases? As quantitativemeasures we use the dilution factor u, Heller's F, and e, which describes how close to the edge ofstate space a feature lies. We find that an IVR threshold can be identified and lies between 250 and300 THz. The threshold is softened because different resonances act at different energies in differentparts of state space. According to our calculation, about 1 in 10~3feature states remains undilutednear the dissociation limit of SCCl_2. This fraction matches the number of sharp spectral featuresobserved recently by experiment when symmetry and Franck—Condon factors are taken intoaccount, and it is in agreement with an analytical model that predicts an increasing fraction ofundiluted features as molecular size increases.