A theoretical study of the electronic spectra of the SiC2H radical

We have performed an ab initio study of the vertical electronic spectra of the lowest-lying doublet and quartet species of the SiC2H system. The ground state presents two species of comparable energy, namely a linear SiC2H(2Π) species and a cyclic SiC2H(2A′) form. The lowest quartet species is SiC2H(4Σ−). We have encountered a rather intense transition in the case of both SiC2H(2Π) (42Π←X2Π, 5.6 eV) and SiC2H(2A′) (72A′←X2A′, 6.3 eV), as well as a number of moderately intense transitions. In the case of SiC2H(4Σ−), we have found only a moderately intense transition, namely 34Π←X4Σ− at 4.9 eV. The lowest-lying excited state of SiC2H(2Π) is 2Δ, which is 3.6 eV higher in energy, while it is 2A″ in the case of the cyclic species and lies more closely at 1.9 eV. In the case of SiC2H(4Σ−), the lowest excited quartet state is 14Π, which is 1.5 eV higher in energy.