The vibration-rotation spectrum of the argon-acetylene van der Waals complex

Abstract

Infrared laser absorption spectroscopy has been carried out on a molecular beam containing the ArHCCH van der Waals complex. Two separate vibrational bands, associated with the monomer Fermi dyad of ν3 and ν2 + ν4 + ν5, were observed. The IR data were analyzed in combination with known microwave frequencies to obtain vibrational origins, rotational constants, and centrifugal distortion constants. The excited vibrational states are characterized by having essentially the same bond lengths, but quite different effective bond angles, relative to the ground state. The large-amplitude bending motions were analyzed with a fixed-separation internal rotation model to provide some angular potential information.