15min:

T. H. LE AND W. R. M. GRAHAM, Molecular Physics Laboratory, Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129.

We report here the first results from a Fourier transform infrared (FTIR) and density functional theory (DFT) study on SiC₅. This species has been produced by ablating a rod made of silicon and graphite powder with a Nd:YAG laser and trapping the products in solid Ar at 15 K. In the only previous observation of SiC₅, McCarthy et al . reported the microwave rotational spectrum. In the present work, extensive FTIR measurements of vibrational frequencies and isotopic shifts from ¹³C enrichment and the naturally occurring ^29,30Si isotopes have been compared with the predictions of density functional theory calculations at the B3LYP/cc-pVDZ level. The excellent agreement between experiment and theory has enabled the assignment of the ₄( ) fundamental of linear SiC₅ at 936.9 \pm 0.2 cm^-1. This information may help in identifying SiC₅ in circumstellar and interstellar environments.