The β⁺ Decay of ²³⁴Np and Other Isospin-Forbidden 0⁺→ 0⁺ Fermi Transitions

Abstract

Although experimental values of the Fermi nuclear matrix elements vary widely from about 1 x 10~3 to 40 x 10"3 for isospin-forbidden 0+ 0+ ß transitions, theoretical calculations using the Coulomb potential and Nilsson wave functions yielded values of MF in reasonably good agreement, except that of 234Np. However, our calculation of MF for this decay as a function of the deformation parameter ß yielded a value of MF in good agreement with experiment for values of ß between 0.1 and 0.2.

Vanishing Fermi to Gamow-Teller Mixing Ratio of the ß+ Decay of 58Co

“…It has been shown [18] that, if a nucleus is deformed, calculations using shell-model wave functions are incorrect because of inhibitions due to the AK selection rule in ß-decay. However, calculations [19][20][21] using the Nilsson model [22] with a one-body spheroidal Coulomb potential to obtain M F seem to give reasonably agreement between theory and experiment, and we shall use the same approach. We assume that the deformed nucleus 58 Co has the rotational band K = 2 and the deformed 58 Fe has K = 0 as shown in Fig.…”