SPECTROSCOPIC EVIDENCE FOR NEAR-RESONANT INTERMOLECULAR ENERGY-TRANSFER IN THE VIBRATIONAL PREDISSOCIATION OF C2H2-HX AND C2H2-DX (X = CL, BR, AND I) COMPLEXES

Infrared laser molecular beam spectroscopy has been used to study a number of C2H2-HX and C2H2-DX complexes. In all cases the asymmetric acetylenic stretch is excited by using an F-center laser while the optothermal method is used to detect the resulting decrease in molecular beam intensity caused by vibrational predissociation of the complex. The spectra are fit to a rigid rotor asymmetric top Hamiltonian to determine the associated molecular constants. Of particular interest is the fact that, for a number of these systems, the vibrational predissociation lifetimes are rather short, despite the remoteness of the intramolecular vibration from the intermolecular bond. The isotopic dependence of these lifetimes suggest that localized intermolecular resonances are responsible for this seemingly anomalous behavior.