Ab initio theory and rotational spectra of linear carbon chains SiC[sub n]S.

On the basis of extensive coupled cluster calculations, the rotational spectra of the linear silicon- and sulfur-containing carbon chains SiC[sub 2n] S (n = 1 -3) in their singlet electronic ground state and SiC[sub 3]S in its triplet electronic ground state have been detected and characterized by means of molecular beam Fourier transform microwave spectroscopy. Rotational and centrifugal distortion constants have been determined to high accuracy as well as the spin-spin coupling constant for triplet SiC[sub 3] S. In addition, the [sup 29]Si, [sup 34]S, and both [sup 13]C isotopic species of SiC[sub 2]S have been detected, allowing the determination of both an effective r[sub 0] structure, as well as a mixed experimental-theoretical structure resulting from the combination of the measured rotational constants with the vibrationrotation coupling constants calculated ab initio. Several rotational satellite lines have also been observed for SiC[sub 2]S and, on the basis of their predicted vibration-rotation and l-type doubling constants, were assigned to the two highest-frequency stretching modes υ[sub 1] and υ[sub 2], and to a progression in the second lowest-frequency bending mode υ 4 up to 3 υ 4. Equilibrium structures and various spectroscopic properties are predicted for all SiC[sub n]S species with n = 1 - 8. [ABSTRACT FROM AUTHOR]