ESR investigation of matrix isolated B 16O and B 17O radicals: Comparison of nuclear hyperfine structure with a b i n i t i o calculations

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Abstract
An extensive ESR investigation of the 2Σ B16O and B17O radicals in rare gas matrices has been conducted. Several different trapping sites in neon matrices have been found and investigated as a function of temperature over the range 3–10 K both during and after deposition. Motional averaging of the nuclear hyperfine tensor seems to be occurring for two neon sites and the argon matrix. The large isotropic boron hyperfine coupling of these sites and the 17O hfs show excellent agreement with ab initio theoretical results. BO radicals trapped in a third neon site do not appear to be undergoing motional behavior. Isotropic and dipolar hyperfine parameters for this site show reasonable agreement with theoretical results. BO radicals in one neon site which is extremely sensitive to temperature effects exhibit nearly perfect ’’single-crystal-like’’ preferential orientation which has not been previously observed in rare gas matrix ESR studies. The results of this BO investigation help to correct erroneous conclusions of an earlier study. Details of the ab initio theoretical methods used to obtain the calculated magnetic parameters are presented. Newly obtained theoretical findings for the related 2Σ AlO radical are compared with previous ESR neon matrix results.