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

Converged close-coupling calculations of the bound rovibrational levels, po sitions and widths of metastable states that predissociate rotationally, vi brationally, and via tunneling, transition intensities, and spectrum shape have been performed starting from accurate ab initio and empirical potentia l energy surfaces for Ar-HD. The computed transitions frequencies agree ver y well with the observed positions of Lines in the recorded near-infrared s pectra [A.R.W. McKellar, Faraday Discuss. Chem. Sec. 73, 89 (1982); J. Chem . Phys. 105, 2628 (1996)]. The agreement of the measured and calculated lin ewidths in the S-1(0) band is also good. Surprisingly, the nb initio potent ial reproduces the observed linewidths somewhat better than the empirical p otential fitted to high-resolution infrared data of Ar-H-2 and Ar-D-2 [C. B issonette et al., J. Chem. Phys. 105, 2639 (1996)]. As a result of the incl usion of some important transitions between the continuum states of the com plex, a very good agreement with experiment is achieved for the shape of th e S-1(0) band of the spectrum. Reliable theoretical predictions of the tran sition energies in the Q(1)(1) band are also reported. (C) 1998 American In stitute of Physics. [S0021-9606(98)01548-7].