ESR Studies of Gamma-Irradiated Crystalline 1-Bromobutane

Abstract

Radiation damage in 1-bromobutane has been studied by ESR spectroscopy. The use of aligned crystals gives well-resolved spectra which can be clearly assigned to the Br2−.. center and the n-butyl radical. Other unidentifiable paramagnetic species are also produced. A quantitative interpretation of the Br2−. spectrum in the parallel orientation gives the magnetic resonance parameters A (81Br) = 472 G and g = 1.992 in satisfactory agreement with previous studies of Br2−. in single crystals of alkali halides. The spectrum of the n-butyl radical shows equal hyperfine interaction with the two β protons and as in other studies this is interpreted in terms of anisotropic internal rotation about the Cα–Cβ bond. The same two paramagnetic species can be identified in the γ-irradiated 1-bromobutane glass, but the ESR spectrum of the n-butyl radical in this case suggests that the internal rotation is frozen out and the radical adopts a nonsymmetrical configuration. Through the positive assignment of the dihalogen anion, the results provide strong confirmation of dissociative electron capture in the radiolysis of this system.