ESR Studies of Gamma-Irradiated Crystalline 1-Bromobutane

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 ${\mathrm{A\; (}}^{81}\mathrm{Br}\text{)\hspace{0.17em}=\hspace{0.17em}472}\mathrm{G}$ and $\text{g\hspace{0.17em}=\hspace{0.17em}1.992}$ 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 $\beta$ protons and as in other studies this is interpreted in terms of anisotropic internal rotation about the C_α–C_β 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.