NEAR-INFRARED LASER SPECTROSCOPY OF THE AR-C2HD COMPLEX - FERMI RESONANCE ASSISTED VIBRATIONAL PREDISSOCIATION

The rotationally resolved infrared spectrum is reported for the C-H st retching vibration of Ar-HCCD. A bending combination band is also obse rved from which we obtain an accurate value for the low-frequency inte rmolecular bending frequency. The vibrational predissociation lifetime of Ar-HCCD is found to be considerably longer than that of Ar-C2H2. T his difference is attributed to the strong Fermi resonance in Ar-C2H2 which is absence in Ar-HCCD. We propose that the perturbing level in t he Ar-C2H2 complex provides a 'doorway' that accelerates the dissociat ion in this system. In Ar-HCCD, where this 'doorway state' is not Ferm i mixed, the dissociation is slower. (C) 1997 Elsevier Science B.V.