Vibrational spectra of penta-atomic silicon–carbon clusters. II. Linear Si2C3

Fourier transform infrared matrix measurements carried out in conjunction with ab initio calculations reported in a companion paper by Rittby have resulted in the first identification of two fundamental vibrations, the C=C stretching mode ν3(σu)=1955.2 cm−1, and the Si–C stretching mode ν4(σu)=898.9 cm−1, of the SiC3Si cluster formed by trapping the products of the vaporization of silicon/carbon mixtures in Ar at 10 K. The observed frequencies, relative intensities, and 13C, 29Si, and 30Si isotopic shifts for the ν3 and ν4 vibrations are in good agreement with the results of the ab initio calculations at the second-order many-body perturbation theory [MBPT(2)] level which predict a linear centrosymmetric geometry for the ground state of SiC3Si. The results of force constant adjustment calculations are consistent with the proposed vibrational assignments and structure.