Matrix isolation electron spin resonance studies of 28,28Si2+, 28,29Si2+, 29,29Si2+, Ge2+, and 73Ge2+ produced by pulsed laser vaporization. Comparison with theoretical calculations

The Si2+ and Ge2+ cation radicals were generated by pulsed laser vaporization and isolated in rare-gas matrices at 4 K for electron spin resonance (ESR) investigations. The electronic ground states were established as X4Σ for both cations with the three unpaired electrons occupying predominantly valence p-type orbitals. In the case of 29Si2+, the observed nuclear hyperfine interaction (A tensor) was compared with that computed in an ab initio configuration interaction type calculation. The dependence of the hyperfine parameters on internuclear distance was also investigated. For comparison purposes, all diatomic and triatomic cations studied in the gas phase and in rare-gas matrices at sufficiently high resolution to observe nuclear hyperfine interaction are listed. For 29Si2+ in neon, gperpendicular = 1.993 (1), |Aperpendicular| = 52.4 (5) MHz, and D = 27.6 (8) GHz; for 73Ge2+, gperpendicular = 1.939 (1) and |Aperpendicular| = 10 (3) MHz