Raman studies of argon dimers in a supersonic expansion. I. Spectroscopy

Abstract

Detection of argon dimers by means of Raman scattering is reported. This first observation of dimers by Raman scattering in a supersonic expansion provides a new technique for the study of the low-lying excitations of dimers and perhaps larger clusters, useful in determining interatomic potentials, etc. Spectra were recorded at low temperature and density in a supersonic expansion of pure argon. Both the pure rotational and the much weaker vibrational Raman transitions were observed for the lowest two vibrational states of the dimer. Raman transition frequencies were determined from the spectra. Theoretical spectra were generated with the use of the polarizability approximation. By using a classical point-dipole-induced dipole model in the calculation of the matrix elements and assuming a thermal distribution over the dimer levels, we could reproduce the rotational spectra to within experimental uncertainty.