Laser spectroscopic study of the SiAr van der Waals complex

Laser fluorescence excitation spectra of the SiAr van der Waals complex, in the vicinity of the Si D-3(degrees)<--P-3 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)Sigma(-) state which correlates with the excited Si(D-3(degrees))+Ar asymptote was assigned, and a rotational and vibrational analysis of the observed bands was carried out. The dissociation energies of the Omega=0(+) components of the ground X (3)Sigma(-) and excited (3)Sigma(-) states were determined [D-0(')=178.8+/-0.4 and D-0(')=122.5+/-0.4 cm(-1)]. Ab initio calculations of SiAr X (3)Sigma(-) and A (3)Pi electronic states correlating with the ground-state Si(3s(2)3p(2) P-3)+Ar asymptote were also carried out. The potential energy curves of the definite-Omega states were computed and used to estimate the dissociation energy, rotational constant, and phenomenological spin-spin interaction in the X (3)Sigma(-) state. These parameters were found to be in reasonable agreement with the experimental determinations. (C) 2002 American Institute of Physics.