FOURIER-TRANSFORM FAR INFRARED-SPECTROSCOPY OF THE UPSILON-3'' VIBRATION OF SIC2 IN AR AT 10K

A Fourier transform study of the vibrational spectrum of SiC2 produced by vaporizing mixtures of silicon and carbon-12 or carbon-13 at 2900 K and quenching the products in argon at 10 K, has enabled the identification for the first time of the ν″3 (b2) vibrational mode, which the results of an earlier matrix study had suggested should lie in the far infrared. The assignment of a frequency observed at 160.4 cm-1 to the ν″3 mode is confirmed by isotopic data and supported by the predictions of ab initio calculations. Optimized force constants have been derived using the frequencies of the newly assigned mode, the previously reported, ν″1 (a1) = 1741.3 and ν″2 (a1) = 824.3 cm-1 vibrations, and their values on single and double carbon-13 substitution. Two models, cyclic and T-shaped, are discussed for the molecule, which is of C2V symmetry. © 1990 American Institute of Physics.