ESR AND OPTICAL SPECTRA OF THE RhC MOLECULE IN INERT MATRICES AT $4^{\circ} K$

Abstract

The RhC molecule in its ground $^{2}\Sigma$ state has been trapped in argon and neon matrices at $4^{\circ} K$ and investigated by ESR and optical spectroscopy. ESR spectra indicate that molecules occupy several different trapping sites in the matrix, and in at least one site, RhC is preferentially oriented. Hyperfine structure constants for interaction with $^{103}Rh$ and $^{13}C$ nuclei and g tensors were determined. In Ar these magnetic parameters are $g_{||}=2.002\ g_\bot=2.059$, $A_{||}(^{103}Rh)= -1147$MHz,\ $A_{\bot}(^{103}Rh) = -1110 MHz,A_{||}(^{13}C) = 91$ MHz, and $A_{\bot}(^{13}C)=52$ MHz . Spin densities at the two nuclei were obtained, and the approximate metal s and d character of the unpaired electron derived. The $^{\bigtriangleup}g_{\bot}$ value is in complete agreement with the spindoubling constant, $\gamma\cap$, for the $X^{2}\Sigma$ state from gas phase spectra, and both indicate that the ground state strongly interacts with an unobserved $^{2}\Pi_{i}$ excited state. A search between 3500 {\AA} and ${35}\mu$ for a transition to this state was unsuccessful, although bands of both the $C^{2}\Sigma\leftarrow X^{2}\Sigma$ transition in the visible and the $A^{2}\Pi_{r}\leftarrow X^{2}\Sigma$ transition in the near infrared were observed in neon matrices.