Pulsed discharge jet electronic spectroscopy of the aluminum dicarbide (AlC2) free radical

摘要

Laser-induced fluorescence and wavelength resolved emission spectra of the C?~2B_2-X?~2A_1 band system of the gas phase aluminum dicarbide free radical have been obtained using the pulsed discharge jet technique. The radical was produced by electron bombardment of a precursor mixture of trimethylaluminum in high-pressure argon. The three vibrational frequencies of T-shaped AlC_2 have been determined in both the combining states along with several of the anharmonicity constants. The 000 band has been recorded with high resolution and rotationally analyzed. The spectrum is complicated by partially resolved spin-rotation and aluminum hyperfine splittings. Where necessary, we have fixed the spin-rotation constants used in the rotational analysis at the values predicted by density functional theory. The derived molecular structures are: r 0″(C-C) = 1.271(2) ?, r 0″(Al-C) = 1.926(1) ?, θ′(C-Al-C) 38.5(2)?, r 0′(C-C) = 1.323(2)?, r 0′(Al-C) 1.934(1) ?, and ′(C-Al-C) = 40.0(2)°. Unlike SiC_2, aluminum dicarbide shows no spectroscopic evidence of facile isomerization to the linear structure in the ground electronic state.