Vibrational spectra of tetra-atomic silicon–carbon clusters. II. Si2C2 in Ar at 10 K

Fourier transform infrared measurements on the spectra of the products of the vaporization of silicon/carbon mixtures trapped in solid argon in concert with ab initio calculations using second order many body perturbation theory have resulted in the identification for the first time of two vibrational fundamentals, ν3(b1u)=982.9 and ν4(b2u)=382.2 cm−1, of the rhombic ground state structure of Si2C2. The observed frequencies, intensities, and isotopic shifts are in good agreement with the ab initio predictions. Tentative assignments are also made for fundamentals of the linear (SiCCSi) and distorted trapezoidal isomers. The relative energies of the three isomers have been estimated at various ab initio levels.