U-238 Mssbauer spectroscopic study of uranium oxysulfide

Masaki, Nobuyuki ; Nakada, Masami  ; Akabori, Mitsuo; Arai, Yasuo; Nakamura, Akio; Sato, Nobuaki*

The U-238 Mssbauer effect of uranium oxysulfide, UOS, has been investigated at various temperatures from 19 K to 80 K. The -ray source used for U-238 Mssbauer spectroscopy was Pu-242 dioxide with high isotope purity. By using a pure Ge detector, the 44.9 keV U-238 Mssbauer -ray is easily distinguished from the 59.5 keV -ray of the Am-241 isotope, which is the daughter nucleus of the isotopic impurity Pu-241. Quadrupole splitting of the U-238 nucleus in UOS is approximately -40 mm/s in the temperature range without account of magnetic splitting. According to neutron diffraction and magnetic susceptibility measurements, UOS is antiferromagnetic at low temperatures with a Neel temperature of T = 55 K. However, Mssbauer spectra below 55 K could be analyzed by using only quadrupole splitting without magnetic splitting. This result showed that the magnitude of quadrupole splitting was much larger than that of magnetic splitting of U nucleus in UOS.