LASER VAPORIZATION GENERATION OF AL12C, AL13C, AL12C2, AND AL13C2 FOR RARE-GAS MATRIX ELECTRON-SPIN-RESONANCE STUDIES - EXPERIMENTAL-THEORETICAL COMPARISONS

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 AlC 2, the spin density resides predominantly in an aluminum 3p z/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). © 1990 American Institute of Physics.