Electron spin resonance in X-irradiated sodium sulphate

Abstract

Electron spin resonance of x-irradiated single crystals of sodium sulphate are obtained at room temperature and the principal g values of the trapped radicals are calculated. Two of the radical ions exhibited isotropic spectral distribution and are identified as SO₃ ^- and O₃ ^-. Two radicals having an anisotropic distribution are identified as SO₂ ^- and SO₄ ^-. The observed 90° period for the angular variation of the spectra of these two radicals is attributed to the presence of two inequivalent sites. The spectra taken in the (111) plane support these observations. Sodium hyperfine splitting is observed with the spectrum of SO₄ ^-. The spectra at liquid nitrogen temperature consisted of two strong isotropic lines attributed to SO₃ ^- and SO₄ ^- and a relatively weak anisotropic line due to O₃ ^-. The experimental results of the group of lines assigned to SO₄ ^- are fitted to a hamiltonian ℋ = H.g.S + I.A.S with S = ½ and I = 3/2 where g values are 2·0337, 2·0271 and 2·0028 and A 26·3, 17·7 and 11·9 Mhz.