Gas phase electronic spectrum of T-shaped AIC₂ radical

Gas phase electronic transitions for the C̃  B22←X̃  A21 and D̃  B21←X̃  A21 band systems of T-shaped AlC2 (C2v) radical have been measured in the 345–475 nm range. Vibrational analyses of both band systems are reported. Simulation of several rotationally resolved bands confirms previously obtained rotational parameters for the C̃  B22 state. The radical is produced by ablating an aluminum rod in the presence of acetylene gas. The resulting supersonic molecular beam is probed using both mass-selective resonant two-color two-photon ionization and laser induced fluorescence. Ab initio calculations and vertical electronic excitation energies help the assignment. Vibrational frequencies for the X̃  A21, C̃  B22, and D̃  B21 states have been determined. Rotational analysis of a number of bands yields spectroscopic constants for one vibronic state in the C̃  B22 manifold and the origin band of the D̃  B21←X̃  A21 system.