New developments in the calculation of βstrength functions
Abstract
We have further developed a QRPA model that uses singleparticle levels and wavefunctions as the starting point for calculating GamowTeller βstrength functions. In our enhanced version Nilsson, WoodsSaxon, or foldedYukawa wave functions and singleparticle energies may serve as the starting point for determining the wave functions of the mother and daughter nuclei involved in the βdecay. Pairing may be treated in either the BCS or the LipkinNogami approximation. To account for the retardation of lowenergy GT decay rates we add, as in the earlier model, a simple residual interaction specific to GT decay, namely V_{GT} = : β^{1} · β^{1+}:, to the hamiltonian. This residual interaction is studied in the RPA approximation. In the case of oddmass nuclei the ∆ν = 0 transitions are generally treated in a firstorder perturbation expansion. We found that these expansions occasionally break down, and have modified them to avoid the singularities. The oddodd case is treated in a way analogous to the odd A case by considering one or the other of the odd particles as a spectator for ∆ν = 0 and both as spectators for ∆ν = 2. As a final extension of the earlier model, we also allow the unpaired odd particle to be in an excited state. We use the enhanced model to calculate GamowTeller βstrength functions, βdecay halflives, and βdelayed neutron emission probabilities for nuclei in several regions of the periodic system, but with the main emphasis on the rareearth region.
 Publication:

Nuclear Physics A
 Pub Date:
 July 1990
 DOI:
 10.1016/03759474(90)90330O
 Bibcode:
 1990NuPhA.514....1M