Knowledge Bank

Subsequent to our spectroscopic detection of the C$2$X (X = P, As) free radicals,} \underline {\textbf{129}} (9600), 2007.} we have studied the electronic spectrum of the jet-cooled $2\Delta$ - $2\Pi$ system of the C$2$P free radical in the 490-630 nm region. High resolution spectra of the two spin-components of the $000$ band of $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}$C$2$P have been recorded, and the rotational and spin-orbit coupling constants have been determined for both electronic states. Evidence of the Renner-Teller effect has been observed in both the $2\Pi$ and $2\Delta$ states, and the vibrational structure has been assigned and fitted to a Renner-Teller hamiltonian for $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}$C$2$P and $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C$2$P. The molecular parameters predicted by density functionl theory are in good agreement with the derived experimental values and provide validation for the spectroscopic assignments. The molecular structure of C$2$P in the ground and excited state will be discussed.