Energy level structure of Sc 42

Abstract

Threshold measurements of the beta decay activity from the residual nucleus in the reaction K 39( α, n)Sc 42 yield a ground state Q value of −7.455±0.030 MeV and energy levels of Sc 42 at 0.526±0.020, 0.600±0.030, 1.42±0.030, 2.22±0.030, 2.96±0.030 and 3.57±0.040 MeV. Position end-point energies calculated from threshold values are 5.525±0.030 MeV for the superallowed decay of the Sc 42 ground level to the Ca 42 ground level and 2.820± 0.030 MeV for the allowed decay of Sc 42m to the 3.191 MeV level of Ca 42. The total cross section is 2.2±0.2 mb for the K 39( α, n)Sc 42 reaction and 6.6±0.6 mb for the K 39( α, n)Sc 42 m reaction at alpha-particle energies 1.45 MeV above the respective thresholds. The half-life is 0.65±0.01 sec for the superallowed decay and 60.6±0.4 sec for the allowed decay. The experimental levels compare reasonably well with those predicted by a jj coupling shell model. The energy difference between the isometric levels of Sc 42 is in accord with a systematic tendency of the energy difference between the lowest T = 0 and T = 1 levels in odd nuclei with N = Z.