The particle-hole interaction and the beta decay of 14B

Abstract

Abstract The last neutron in 14B necessarily occupies an orbit in the sd shell and hence the allowed β-decay to negative parity states of 14C is primarily sensitive to the interaction between nucleons from the p and sd shells (the particle-hole interaction). A particle hole-interaction has been derived which gives a good account of the non-normal parity states of a number of nuclei from 11Be to 16O. The important features of this interaction are that it remains close in character to a realistic G-matrix interaction and that it reproduces two specific characteristics of the nuclear level spectra; (i) the relative separation of the 1 s 1 2 and 0 d 5 2 single particle orbits as a function of mass number which is found to be sensitive to the non-central components of the interaction and is adequately reproduced by the bare G-matrix and (ii) the separation of multiplets of different isospin which is incorrectly reproduced by the bare G-matrix. The failure of the G-matrix in the latter case is remedied by adding a repulsive component to the triplet-odd central force. This interaction is shown to give a good description of the allowed β-decay of 14B to the lowest 1−, 2− and 3− levels of 14C. The unique first-forbidden decay to the 14C ground state is predicted to be weak as the result of a cancellation in the matrix element. No significant strength is predicted for decay to states of 14C which are unstable with respect to neutron emission. It is shown that certain features of the β-decay may be simply understood when the wave functions are expressed in a weak coupling basis and also in a basis classified according to the supermultiplet and SU(3) quantum numbers.