EXPLORING MOLECULAR VIBRATIONAL MOTIONS WITH PERIODIC-ORBITS

The theory of periodic orbits for conservative Hamiltonian systems and the way that it is applied to analyse vibrational spectra of highly e xcited polyatomic molecules is reviewed. Applications for triatomic, t etratomic molecules and van der Waals clusters are presented. It is sh own that the periodic orbit method can trace localized eigenfunctions above potential barriers which are associated with saddle-node bifurca tions. Such states connect separate minima on the potential energy sur face, and thus, are important for studying isomerization processes.