Knowledge Bank

Laser fluorescence excitation spectra of the SiAr van der Waals complex, in the vicinity of the Si $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}D0\leftarrow \mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}P$ atomic resonance transition near 220.7 nm are reported. At low resolution, a single excited state $(v\prime ,0)$ 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 $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Sigma -$ state which correlates with the excited $Si(\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}D0)+Ar$ 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 $X3\Sigma -$ and excited $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Sigma -$ states were determined [$D0\prime \prime =178.8\pm 0.4$ and $D0\prime =122.5\pm 0.4cm-1$]. Ab initio calculations of the SiAr $X3\Sigma -$ and $A3\Pi$ electronic states correlating with the ground-state $Si(3s23p2\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}P)+Ar$ 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 $X3\Sigma -$ state. These parameters were found to be in resonable agreement with the experimental determinations.