Research Papers in Physics and Astronomy


Date of this Version

January 1954


Published in Physical Review 93:1 (January 1, 1954), pp. 155-159. Copyright ©1954 The American Physical Society. Used by permission. Online at URL:


The radiations from Sm153 and Eu155 have been studied by means of a 180-degree, magnetic-focusing, variable-field beta-ray spectrometer-spectrograph using enriched materials. In the disintegration of 47.0-hr Sm153, conversion electrons of three gamma rays of energy, 0.0691, 0.1027, 0.548 Mev, and three beta-ray spectra whose end-point energy and relative intensity were 0.255 Mev, 9 percent; 0.685 Mev, 70 percent; 0.795 Mev, 21 percent, respectively, were observed. A fourth beta-ray spectrum of end-point energy 0.62 Mev and intensity less than 6 percent is postulated. A decay scheme in good agreement with these data and with nuclear shell theory is proposed in which spin and parity have been assigned to all levels. The discrepancy between the magnetic moment measurement and the requirements of shell theory as to the parity of the ground state of Eu153 has been resolved in favor of shell theory. In the disintegration of Eu155 two betaray spectra of end-point energy 0.152 and 0.252 Mev and relative intensity 84 percent and 16 percent, respectively, and conversion electrons of four gamma rays of energy 0.0593, 0.0858, 0.1045, 0.1309 Mev were observed, in agreement with earlier work. Weak conversion-electron lines attributed to gamma rays of energy 0.0187 and 0.1368 Mev were also observed.

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