Isobaric Analog States and Coulomb Displacement Energies in the (1d52) Shell
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The (p,t) and (p, He3) reactions have been used to locate three previously unknown T=32 isobaric analog states in F19, Ne19, and Mg23, in addition to significantly improving the precision on the energies of the T=32 state in Na23 and the T=2 states in F20 and Na24. These multiplets all lie within the "(1d52) shell" in that they have fewer than n=12 nucleons outside O16, and Tminimum (12n,6-12n). Including these data, twenty-eight displacement energies are now known throughout this shell for all possible multiplets with T2 (except T=2, mass-22). The experimental displacement energies were compared in detail with calculations which used Hecht's Coulomb-energy equations; the excellent agreement obtained appeared to be relatively insensitive to the assumed nuclear wave functions since both the low-seniority j-j coupling limit and the Wigner supermultiplet scheme produced similar results. Four parameters related to the two-body Coulomb-energy matrix elements were treated as adjustable in fitting the data but their final values are in reasonable agreement with matrix elements calculated using harmonic-oscillator wave functions. A fifth adjustable parameter took account of the Z and N dependence of the charge radius. Using the experimental parameters, the unmeasured masses of Na19, Mg20, Mg21, Al22, Al23, Si24, and Si25 are predicted, together with the excitation energies of unobserved analog states in the 1d52 shell. 1969 The American Physical Society.
