An ESR study at 77 K of the bromine atom and the gsim;Nndash;Brminus;sdot; sgr;ast; radical in xhyphen;irradiated Nndash;bromosuccinimide single crystals

摘要

Two radicals have been identified from an ESR study of Nndash;bromosuccinimide single crystals xhyphen;ray irradiated at 77 K. One is the previously studied sgr;ast; radical fromed by an electron attachment to the antibonding orbital of the Nndash;Br bond in Nndash;bromosuccinimide and the other is a bromine atom. Analysis shows that the sgr;ast; radical interacts with a neighboring proton to give a large proton superhyperfine coupling of (37, 26, 21)G and it has suggested that the gsim;Nndash;Br group is nonplanar. The bromine atom which apparently originates from the cation precursor exhibits a very largeganisotropy of (1.837, 2.384, 2.430) and a bromine 81 coupling of (+510, +183, +209)G. It has been found from thegand hyperfine coupling tensors that the crystal field splitting (Dgr;=4200 cmminus;1) is about the same order as the spinndash;orbit coupling (lgr; =2456 cmminus;1) and that the spin densities in the 4pand 4sorbitals are estimated to be close to unity and 0.004, respectively. The geometry of the trapping site has been deduced by comparing the crystallographic coordinates with the principal directions of thegandAtensors.