High-resolution, rotationally resolved electronic spectroscopy of the MgNCradical

High-resolution, rotationally resolved, laser-induced fluorescence (LIF) sp ectra for the origin band, as well as several transitions involving vibrati onally excited levels of the (A) over tilde(2)Pi <-- (X) over tilde(2)Sigma (+) electronic transition of the MgNC radical, have been recorded using the output of a pulse-amplified Ti:Sapphire ring laser. The MgNC radical was g enerated in a supersonic free jet expansion by simultaneous laser ablation of a magnesium rod and photolysis of acetonitrile (CH3CN). Rotational analy sis yielded molecular constants for both the ground and excited states of t he studied vibronic transitions. The molecular constants for the vibrationl ess state of the (X) over tilde state are in excellent agreement with previ ous microwave studies of MgNC. Since the (A) over tilde electronic state of MgNC is a linear (2)Pi state, the bending vibronic level structure is subj ect to both Renner-Teller and spin-orbit coupling. Suggested vibronic assig nments of the observed transitions, made considering both these interaction s and with the aid of the rotational analysis, are discussed. (C) 1999 Acad emic Press.