Gas phase electronic spectrum of T-shaped AlC2 radical

Gas phase electronic transitions for the C approximate to B-2(2)<- X approximate to (2)A(1) and D approximate to B-2(1)<- X approximate to (2)A(1) band systems of T-shaped AlC2 (C-2v) 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 C approximate to B-2(2) 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 X approximate to (2)A(1), C approximate to B-2(2), and D approximate to B-2(1) states have been determined. Rotational analysis of a number of bands yields spectroscopic constants for one vibronic state in the C approximate to B-2(2) manifold and the origin band of the D approximate to B-2(1)<- X approximate to (2)A(1) system.