Paramagnetic Centers in Irradiated Potassium Sulfate

Abstract

Recent investigations (1, 2) into the radiolysis of polycrystalline sulfates prompted this examination of the electron spin resonance ( e a r . ) spectra of irradiated potassiuin sulfate single crystals. By irradiating the samples and studying their spectra a t 77 OK and a t 300 OK different stages in the radiation daiiiage process were revealed. The e.s.r. spectra of single crystals of I<2S04 irradiated and examined a t 77 OK deinonstrated the presence of a single paramagnetic species, A, characterized by a highly anisotropic g-tensor. By monitoring the spectrum during warm-up of tlie sample it could be seen that over 90% of A deconiposed to form a second species, B, although tlie amount of A surviving a t 300 "I< was sufficient t o permit the deterinination of its g-tensor a t this temperature. The radical B was characterized by an almost isotropic g-tensor. The principal values of the g-tensors of the two radicals are given in Table I. Examination of a very large, heavily irradiated crystal revealed 33S hyperfine structure in the spectrum of radical B, the interaction being 273, 270, and 315 i\/Ic/s witli Ho along the a , b , and c crystallographic axes respectively. No 33S hyperfine structure was detected in the spectrum of radical A. I-Io~vever, since a very inucli siiialler crystal had to be used for experiments a t 77 OK, the anticipated signal/noise ratio \\.as less than 5: 1, and so the absence of 33S signals was not proved unequivocally.The maximum-slope line ~vidths of the spectra of botli radicals Ivere approximately 5 G , and were independent of temperature. The major contributions to the line ~~i d t h s are therefore presumed to be crystal iinperfections and unresolved 3"1( hyperfine structure.The identification of the two radicals trapped in irradiated II(zS04 depended on a comparison of their spectral paraiiieters ~~i t l i those of already well-substantiated species, and it was concluded that A and B \Irere S o 4 and SO3-respectively.

Etude Spectrometrique De La Lazurite Du Pamir, Tajikistan

“…Le centre II de la lazurite peut être attribué à l'ion radical SO 4 -, qui a déjà été observé dans d'autres composés (Gromov & Morton 1966, Samoilovich 1971, comme, par exemple, dans la sodalite synthétique (Tableau 3) avec une impureté de soufre (McLaughlan & Marshall 1970). Nous pouvons supposer que les ionsradicaux moléculaires S 3 et SO 4 -(les centres colorés) se forment et sont stables pendant les réactions de réduction des oxydes de soufre qui ont lieu lors de la formation de la lazurite naturelle (Samoilovich et al 1973).…”

E.S.R. of X-irradiated Na2SO4 doped with NaClO4

“…A comparison of the principal g components of these two radicals with those reported earlier [8,9] shows that they are SO 4-radicals trapped at two chemically inequivalent sites. In pure Na2SO 4 irradiated with X-rays no such chemical inequivalenee was observed.…”

“…The sodium atoms are along the C axis. The projections of the unit ceil onto the three crystallographic planes have been given earlier [4,8]. Single crystals of N%SO4 doped with NaC104 were grown at 35~ by slow evaporation of an aqueous solution of the reagent grade Na2SO~ with a smalt percentage of NaC104 as impurity.…”

Spectroscopic studies and electrical conductivity behavior of γ-irradiated Li2SO4—Na2SO4mixed system

“…EPR of SO, in single crystals has been reported in LiNaS04 [27, 281. The SO, free radical is identified by EPR from its g-values [30].…”