Laser vaporization generation of Al12C, Al13C, Al12C2, and Al13C2 for rare gas matrix electron spin resonance studies: Experimental–theoretical comparisons

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Abstract
The metal carbide radicals AlC and AlC2 have been generated by the laser vaporization of aluminum carbide and trapped in neon and argon matrices at 4 K for electron spin resonance (ESR) characterization. These results provide the first experimental evidence showing that AlC has a 4Σ ground electronic state and that AlC2 is X 2A1. Ab initio theoretical calculations were conducted for the geometries and various nuclear hyperfine parameters in both radicals which yielded A values in reasonable agreement with the observed. In AlC, the three unpaired electrons reside primarily on carbon with the following neon matrix magnetic parameters (MHz): g∥=2.000(1); g⊥=2.0010(5); ‖A⊥(Al)‖=33.2(5); ‖A∥(Al)‖=3(3); A⊥(13C)=52.1(5); A∥(13C)=52(2); and D(zero field splitting)=374(1). For AlC2, the spin density resides predominantly in an aluminum 3pz/3s hybrid directed away from C2. The neon magnetic parameters (MHz) are: g∥=2.0005(5); g⊥=1.9965(3); A⊥(Al)=941.5(5); A∥(Al)=1067(1); ‖A∥(13C)‖=59(1); and ‖A⊥(13C)‖=52(1).