Laser spectroscopic study of the SiAr van der Waals complex

Abstract

Laser fluorescence excitation spectra of the SiAr van der Waals complex, in the vicinity of the Si D°3←3P 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 Σ−3 state which correlates with the excited Si(3D°)+Ar asymptote was assigned, and a rotational and vibrational analysis of the observed bands was carried out. The dissociation energies of the Ω=0+ components of the ground X 3Σ− and excited Σ−3 states were determined [D0″=178.8±0.4 and D0′=122.5±0.4 cm−1]. Ab initio calculations of SiAr X 3Σ− and A 3Π electronic states correlating with the ground-state Si(3s23p2 3P)+Ar asymptote were also carried out. The potential energy curves of the definite-Ω states were computed and used to estimate the dissociation energy, rotational constant, and phenomenological spin–spin interaction in the X 3Σ− state. These parameters were found to be in reasonable agreement with the experimental determinations.