Near-infrared absorption spectrum of the Ar–HD complex: Confrontation of theory with experiment

Abstract

Converged close-coupling calculations of the bound rovibrational levels, positions and widths of metastable states that predissociate rotationally, vibrationally, and via tunneling, transition intensities, and spectrum shape have been performed starting from accurate ab initio and empirical potential energy surfaces for Ar–HD. The computed transitions frequencies agree very well with the observed positions of lines in the recorded near-infrared spectra [A.R.W. McKellar, Faraday Discuss. Chem. Soc. 73, 89 (1982); J. Chem. Phys. 105, 2628 (1996)]. The agreement of the measured and calculated linewidths in the S1(0) band is also good. Surprisingly, the ab initio potential reproduces the observed linewidths somewhat better than the empirical potential fitted to high-resolution infrared data of Ar–H2 and Ar–D2 [C. Bissonette et al., J. Chem. Phys. 105, 2639 (1996)]. As a result of the inclusion of some important transitions between the continuum states of the complex, a very good agreement with experiment is achieved for the shape of the S1(0) band of the spectrum. Reliable theoretical predictions of the transition energies in the Q1(1) band are also reported.