Richard J. Nagle

Isospin conservation in the β-decay of Sc44, Zr95 and Nb95

The angular correlation between β rays and circularly polarized γ rays has been measured by the method of rapid alternation in the cases of Sc44, Zr95 and Nb95. The present result for Sc44 indicates that the Fermi matrix element is very small or zero, within experimental error. This agrees with results obtained previously at this laboratory for Sc46 and A41 (also by the method of rapid alternation), but disagrees with the measurement of Boehm and Wapstra. In the case of Zr95 excellent agreement is obtained with the results of Appel and Schopper, but a different interpretation of the results is offered here which eliminates the need for their conclusion that interference exists between the Gamow-Teller and Fermi transitions. Our interpretation requires (as theirs does) that at least one of the pertinent excited states in Nb95 has spin 72 (preferably the 726-keV state). The agreement between theory and the measurement is then very close and requires almost no mixingin any of the radiations. Nb95, measured for the first time here, decays a pure Gamow-Teller (ΔJ = 1) transition followed by an almost pure M1 radiative transition. In this case no other alternative has any reasonable probability. The spin of the level at 762 keV in Mo95 is 72, and the spins of Sc44 and the level at 1.16 MeV in Ca44 are definitely 2.