Radiations from RaD and RaE

Abstract

The electron and gamma-spectra from RaD and RaE have been thoroughly investigated. The gamma-radiation from RaD was studied with both krypton and argon proportional counters with brass and aluminum cathodes. The L alpha, L beta, and L gamma radiations of Bi were observed and identified with a critical absorber. The intensity ratios of L alpha:L beta:L gamma are 1:1:0.2. The previously reported 7.8-kev (10 percent) line was not found but could be strongly excited by copper backing. The weak 23-kev line (10^-3 per disintegration in our measurements) could be contributed from the piling effect of the detecting system. The conversion electrons of RaD were investigated in a solenoid magnetic spectrometer to obtain the L and (M+N) conversion coefficients. The results are: NeL / N beta =64 percent, NeM+N / N beta =21 percent, NeL+M+N / N beta =(85±5) percent. The conversion electrons of RaD were again investigated with a 180° beta-spectrometer with a resolution of 0.8 percent and a counter window of ~6 µg/cm2. The LI, LII, and LIII conversion lines of the 46.5-kev gamma-ray were resolved. The ratio of LI:LII:LIII:MI-III:MIV-V:NI-V:NVI-VIII+0 are 1:0.075:0.007: 0.25:0.006:0.07:0.007. From the ratios of the L-subshell conversion electrons, the 46.5-kev transition is interpreted as an M1 type. The upper limit of the intensity of the reported lines at 42 kev, at 37 kev, and at 31 kev must be less than 0.5 percent per disintegration if the same conversion coefficient is assumed. The unconverted 46.5-kev gamma-radiation is 0.07±0.02 per disintegration. Thus the excited state of 46.5 kev in RaE can account for (92±5) percent of the disintegrations. Neither internal conversion electrons nor nuclear gamma-radiations are found in RaE. A faint x-ray (~80 kev) of the order of 10-4 per disintegration due to the ionization effect was observed in RaE. A brief discussion of the decay scheme of RaD and the possible spin assignments of various levels is included.