INFRARED SPECTROSCOPY OF CARBON- AND CARBON-SILICON CLUSTERS

Abstract

Many of the molecules found in space are carbonaceous, that is, they have a carbon backbone in their structure. In addition, many of these molecules carry heteroatoms such as nitrogen and oxygen and also second row elements such as silicon. To date, four silicon-carbon molecules SiC$_n$ ($n=1-4$) have been detected in space and several more by high-resolution spectroscopic techniques in the laboratory. Owing to their symmetry, many clusters of the form SiC$_n$Si (and linear C$_n$ chains) are non-polar and hence have no pure rotational spectrum. In an effort to obtain the gas-phase spectra of these clusters in the infrared, we have started a dedicated laboratory program employing diode laser techniques and more recently an optical parametric oscillator-based spectrometer operating at 5 microns, where many carbon- and carbon-silicon chains are expected to exhibit strong infrared-active vibrational modes. Results from new observations of the previously studied Si$_2$C$_3$ and C$_6$ clusters \textbf{101}, 10237 (1994).}$^,$ \textbf{79}, 769 (1993).} will be reported.