ELECTRONIC SPECTRUM OF THE AlC$_2$ RADICAL

Abstract

An electronic transition of the AlC$2$ radical (\emph{C}${2v}$ structure) has been observed using laser induced fluorescence spectroscopy. The molecule was prepared in a supersonic expansion using laser ablation of an aluminum rod in the presence of acetylene gas. A spectrum was recorded and assigned to the $\tilde{C}$ $^2$B$_2$ - $\tilde{X}$ $^2$A$_1$ system based on a rotational analysis and agreement with calculated molecular parameters and excitation energies. \emph{Ab initio} results are in accord with previous theoretical studies which conclude that AlC$2$ possesses a triangular \emph{C}${2v}$ $^2$A$1$ geometry, with the linear \emph{C}${\infty v}$ $^2$$\Sigma$$^+$ AlCC isomer 0.70 eV higher in energy. A spectral fit yields molecular constants both in the ground and electronically excited states.