Neon matrix ESR investigation of \u3csup\u3e12\u3c/sup\u3eC\u3csup\u3e+\u3c/sup\u3e\u3csub\u3e2\u3c/sub\u3e and \u3csup\u3e13\u3c/sup\u3eC\u3csup\u3e+\u3c/sup\u3e\u3csub\u3e2\u3c/sub\u3e : Confirmation of a \u3csup\u3e4\u3c/sup\u3e\u3cem\u3eΣ\u3csup\u3e-\u3c/sup\u3e\u3csub\u3eg\u3c/sub\u3e\u3c/em\u3e ground electronic state

The 12C+2 and 13C+2 cation radicals have been isolated in neon matrices by the photoionization of C2(g) generated by the laser vaporization of thin carbon disks. A new procedure of supporting and thermally outgassing such targets for laser vaporization ESR studies in rare gas matrices is described. The ESR results confirm the4Σ-g ground electronic state assignment for C+2 and provide a valence orbital electronic structure characterization based on the 13C hyperfine structure (hfs). The ESR lines are extremely narrow for a high-spin powder sample and an intense off-angle or extra- absorption feature exibits unusual hfs. Normally forbidden (ΔMS\u3e1) transitions were detected at low magnetic fields. The magnetic parameters for 13C+2 in a neon matrix at 4 K are: D=3668(3) MHz; g⊥ =2.0018(5); g‖ =2.0023(5); ‖A‖‖ =99.4(8) MHz; and ‖A⊥‖ =95.2(5) MHz