15min:

CHONG TAO, ALEXEY TESLJA AND PAUL J. DAGDIGIAN, Department of Chemistry, The Johns Hopkins University, Baltimore, Md 21218-2685; SULE ATAHAN AND MILLARD H. ALEXANDER, Department of Chemistry and Biochemistry, The University of Maryland, College Park, MD 20742-2021.

Laser fluorescence excitation spectra of the SiAr van der Waals complex, in the vicinity of the Si ³D^{o 3}P atomic resonance transition near 220.7 nm are reported. At low resolution, a single excited state (v',0) progression of bands terminating in a dissociation continuum is observed. Several weaker bands associated with many of these strong bands are found in scans at higher resolution. A transition to an excited ^{3 -} state which correlates with the excited Si(³D^o)+Ar asymptote was assigned, and a rotational and vibrational analysis of the observed bands was carried out. The dissociation energies of the =0⁺ components of the ground X ^{3 -} and excited ^{3 -} states were determined [D₀'' = 178.8 \pm 0.4 and D₀' = 122.5\pm0.4 cm^-1]. Ab initio calculations of the SiAr X ^{3 -} and A ³ electronic states correlating with the ground-state Si(3s²3p^{2 3}P) + Ar asymptote were also carried out. The potential energy curves of the definite- states were computed and used to estimate the dissociation energy, rotational constant, and phenomenological spin-spin interaction in the X ^{3 -} state. These parameters were found to be in resonable agreement with the experimental determinations.