K-electron capture probabilities in the decays of Gd151 and Dy159

Abstract

The K-electron capture probability, PK, in the allowed and non-unique firstforbidden transitions is measured by observing coincidences between K x rays and y rays. The following results are obtained. In Gd lsl decay PK to the 349.8 keV level is 0.713 + 0.015 and PK to the 307.4 keV level is 0.813 + 0.020. It is also deduced that the decay energy Q~c is 491 + _ 19 " keV and the spin of the 307.4 keV level is 7/2. In Dy ls9 decay PK to the 58.0 keV level is found to be 0.803 +_ 0.032.

Atomic masses of rare earth isotopes145Pm,145Sm and151Gd, derived from decay measurements of145Sm and151Gd

“…These difficulties are overcome in the relative measurement. We have tentatively used the reported PK-values of the decay branches leading to the 350keV and 308keV states in t51Eu, P~50= 0.713 (15) and P3~ =0.810 (20) [3] and have derived from the ratio of these values a value of the decay energy in agreement with our result. We have derived from the presently determined decay energies and the experimental values listed in Table 1, …”

“…1 is removed. The presently measured decay energy of ~ 51Gd is substancially smaller than the earlier experimental values [3,4]. One of these results [4] has been obtained with the summing technique.…”

“…i discrepancies have been reported [1]: the experimental decay energies of 145Sm [2] and 151Gd [3,4] not agree with the mass differences obtained from other measurements. A compilation of these experimental results is given in Table 1.…”

“…We have measured this correction separately and found an agreement with the more accurate coincidence measurement. Further, the measurement of absolute Pr-values has been used earlier [3]. In this experiment the knowledge of detection-and coincidence efficiency and of the fluorescence yield was required.…”