The role of the aluminosilicate matrix in the gamma-irradiation energy transfer to the oxalate molecule

Abstract

Three types of aluminosilicate matrices, prepared from oxalate solutions, were γ-irradiated and investigated by ESR spectroscopy. In the aluminosilicates with Al:Si = 1:1 that can be considered as the end member of allophane series upon γ-irradiation at room temperature in the presence of air, no stable paramagnetic species were formed, even if the aluminosilicate was precipitated in the presence of oxalate. On the other hand, in the evacuated sample upon γ-irradiation at room temperature a single line ESR spectrum at g = 2.0036 was detected that was ascribed to oxalate radical ▪ Oxalate radical was observed in the other two types of aluminosilicates even in the presence of air. Upon γ-irradiation at 77 K, in addition to the described oxalate radical, primary irradiation sites were observed and identified as paramagnetic centres derived from chlorides and hydrogen atoms. Radicals from chlorides were observed in all samples except in NaAl(OH) 4(H 4SiO 4) 2 (hydrous feldspathoid), the same as were found recently in protoimogolite allophane. Hydrogen atoms were found in Al(OH) 3 · H 4SiO 4 and NaAl(OH) 4(H 4SiO 4) 7. The results suggest that oxalate acts as a trap for γ-irradiation energy.