ANHARMONICTTY OF TILE VIBRATIONS OF $SiC_{2}$ AND $Si_{2} C$ AT 2000

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1994

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Ohio State University

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Butenhoff and $Rohlfing^{1}$ report that $SiC_{2}$ has an anharmonic ground state, based on Laser-induced fluorescence studies. Presilla-Marquez and $Graham^{2}$ report that $SiC_{2}$ is a floppy molecule with a bending frequency of $166 cm^{-1}$. Therefore $SiC_{2}$ and perhaps $Si_{2}C$ may have some anharmonic behavior which can show up in Kundsen effusion mass spectrometric studies as is the case for $C_{3}$. A thorough Knudsen-effusion mass spectrometric study of $SiC_{2}$ and $Si_{2}C$ was carried out: a total of 46 data sets of $SiC_{2}$ and 52 data seta of $Si_{2}C$ over a temperature range of 1760-2080 K were obtained. Although the main objective of this study was to measure the atomization enthalpies of small silicon-carbide clusters; we also wanted to determine the effect of any anharmonic of $SiC_{2}$ and $Si_{2}C$ on the experimental result, ~2000 K. Atomization enthalpies of $\Delta H_{a,0}=1247 \pm 7$ and $\Delta H_{a,0}=1048 \pm 10$ kJ $mol^{-1}$ are selected for $SiC_{2}$ and $Si_{2}C$.

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1. T. J. Butenhoff and E. A. Rohlfing, J. Chem. Phys. 95, 1 (1991). 2. J. D. Presilla-Maiquez and W. R. M. Graham. J. Chem. Phys. 95, 5612 (1991).
Author Institution: Dept. of Chemistry, Texas A\&M University, College Station

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