J. D. PRESILLA-MÁRQUEZ, C. M. L. RITTBY AND W. R. M. GRAHAM, Department of Physics, Texas Christian University, Fort Worth, TX 76129.

Ongoing Fourier transform infrared investigations of the spectra and structures of silicon-carbon clusters trapped in Ar at 10 K, have resulted in the observation of the first six-member cluster, Si₂C₄ cluster. Two vibrational fundamentals of the linear SiC₄Si structure have been assigned, the C=C stretching mode ₄(_u) = 1807.4 cm^-1, and the Si-C stretching mode ₅(_u) = 719.1 cm^-1. The measured frequencies, relative intensities, and ¹³C and ^29,30Si isotopic shifts are in very good agreement with the predictions of DFT calculations and confirm the previously predicted, linear symmetric geometry for the ground state of SiC₄Si.