SPECTRA OF PtC AND RhC

Author Institution: Institute of Physics, Vanadisv\""agen 9, University of StockholmIn a King furnace we have obtained the molecules PtC and RhC in the gaseous phase. The absorption spectra of these molecules were taken in a large concave grating spectrograph. The isotope splitting in the Pt-molecule confirms that the molecule must be attributed to PtC. The Rh spectrum was obtained under the same experimental conditions. This fact, together with the magnitudes of the molecular constants, makes it very unlikely that the absorber is anything other than RhC. Rotational analysis has been carried out for both molecules. In PtC two systems have been analysed, one $^{1}\Pi-^{1}\Sigma$ and one $^{1}\Sigma-^{1}\Sigma$, with the lower $^{1}\Sigma$ state in common. In RhC four states have been studied. Three of them are $^{2}\Sigma$ states, one is a $^{2}\Sigma$ state. The lowest state is a $^{2}\Sigma$ state. The two excited $^{2}\Sigma$ states strongly interact with each other. The following molecular constants in $cm^{-1}$ have been derived for the lowest states. $\begin{array}{llll}&Ptc &RhC\\\omega_{o}&1051.18 &1049.87\\ \omega_{o}X_{v} & 4.87 & 4.94\\ B_{o}&0.5303 &0.6027\\\alpha_{o}&0.0032 &0.00396\end{array}