Ab initio ro-vibronic spectroscopy of SiCCl (X̃(2)Π).

The full dimensional potential energy surfaces of the (2)A' and (2)A'' electronic components of X̃(2)Π SiCCl have been computed using the explicitly correlated coupled cluster method, UCCSD(T)-F12b, combined with a composite approach taking into account basis set incompleteness, core-valence correlation, scalar relativity, and higher order excitations. The spin-orbit and dipole moment surfaces have also been computed ab initio. The ro-vibronic energy levels and absorption spectrum at 5 K have been determined from variational calculations. The influence of each correction on the fundamental frequencies is discussed. An assignment is proposed for bands observed in the LIF experiment of Smith et al. [J. Chem. Phys. 117, 6446 (2002)]. The overall agreement between the experimental and calculated ro-vibronic levels is better than 7 cm(-1) which is comparable with the 10-20 cm(-1) resolution of the emission spectrum.