Matrix-isolation investigation of the diatomic anion radicals of aluminum and gallium (Al-2(-) and Ga-2(-)): An electron spin resonance and ab initiotheoretical study

The diatomic aluminum and gallium anion radicals (Al-2(-) and Ga-2(-)) have been studied by electron spin resonance (ESR) as isolated ions in neon mat rices near 4 K. Apparently no previous examples of purely metallic anions h ave been studied by the rare gas matrix isolation trapping technique with a ny type of spectroscopic method. Pulsed laser ablation of the metals was th e experimental generation method which has enabled the first direct charact erization of the ground electronic states of these anions. The X (4)Sigma a ssignment agrees with previous interpretations of photoelectron spectroscop ic results. The analysis of fine structure and nuclear hyperfine interactio ns has yielded a detailed description of the electronic structure in these seven-valence electron anion radicals, with comparisons to other isovalent X (4)Sigma radicals presented. Experimental values of the nuclear hyperfine interactions (A tensors) were compared with theoretical results obtained f rom various ab initio computational methods, including configuration intera ction and density functional theory. Reasonable agreement between these exp erimental results and theoretical predictions was observed. (C) 2001 Americ an Institute of Physics.