VIBRATIONAL-SPECTRA OF PENTA-ATOMIC SILICON-CARBON CLUSTERS .3. PENTAGONAL SI3C2

Fourier transform infrared measurements on the spectra of the products of the vaporization of silicon/carbon mixtures trapped in argon at si milar to 10 K combined with the results from a published ab initio stu dy and from new theoretical calculations carried out in the present wo rk, have resulted in the first observation of a spectrum for the penta gonal Si3C2 cluster. Three vibrational fundamentals have been assigned : the v(2)(a(1)) symmetric ''breathing'' vibration at 681.1 cm(-1), th e v(7)(b(2)) Si-alpha-C-C-Si-alpha stretching deformation at 956.7 cm( -1) and the v(8)(b(2)) C-Si-beta-C antisymmetric stretching vibration at 597.8 cm(-1). The observed frequencies, relative intensities, and C -13, Si-29, and Si-30 isotopic shifts are in excellent agreement with the theoretical predictions. (C) 1996 American Institute of Physics.