title: Electronic spectrum of the AlC(2) radical.
abstract: An electronic transition of the AlC2 radical (C2v structure) has been observed using laser-induced fluorescence spectroscopy. The molecule was prepared in a supersonic expansion by ablation of an aluminum rod in the presence of acetylene gas. A spectrum was recorded in the 451-453 nm region and assigned to the C 2B2-X 2A1 system (T0 = 22,102.7 cm(-1)) based on a rotational analysis and agreement with calculated molecular parameters and excitation energies. Ab initio results obtained using couple cluster methods are in accord with previous theoretical work which concludes that ground-state AlC2 possesses a T-shaped C2v 2A1 geometry, with the linear 2Sigma+ AlCC isomer 0.70 eV higher in energy. A fit of the experimental spectrum yields rotational constants in the ground and electronically excited states that are in reasonable agreement with the calculated values: A'' = 1.7093(107), B'' = 0.4052(50), C'' = 0.3228(49) cm(-1) for the X 2A1 state, and A' = 1.5621(137), B' = 0.4028(46), C' = 0.3201(54) cm(-1) for C 2B2. Variation in individual fluorescence lifetimes suggests that the emitting C 2B2 state undergoes rovibronic mixing with lower lying electronic states.
authors.affiliation: Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056, Basel, Switzerland.
authors.forename: Egor
authors.initials: E
authors.lastname: Chasovskikh
authors.forename: Evan B
authors.initials: EB
authors.lastname: Jochnowitz
authors.forename: Eunsook
authors.initials: E
authors.lastname: Kim
authors.forename: John P
authors.initials: JP
authors.lastname: Maier
authors.forename: Isabelle
authors.initials: I
authors.lastname: Navizet