EVAN B. JOCHNOWITZ, EGOR CHASOVSKIKH, EUNSOOK KIM AND JOHN P. MAIER, Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland; ISABELLE NAVIZET, Laboratoire de Chimie Théorique, Université de Marne-la-Vallée, F-77454 Champs sur Marne, France.

An electronic transition of the AlC2 radical ( 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 C 2B2 - X 2A1 system based on a rotational analysis and agreement with calculated molecular parameters and excitation energies. Ab initio results are in accord with previous theoretical studies which conclude that AlC2 possesses a triangular C 2v 2A1 geometry, with the linear C infinity 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.