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Abstract:

Recent on-line nuclear orientation measurements of odd-A nuclear magnetic dipole moments of odd-A Sb, Te and I isotopes by the method of NMR on oriented nuclei mean that we now have complete series of odd-A moments up to, and including, those closest to the double shell closure at 132Sn. In this paper we consider the systematic changes in the measured moments as a function of proton number for the isotonic sequence 133Sb [g7/2+]1-139La [g7/2+]7 and as a function of neutron number for the isotopic sequences 125-133Sb and 127-135I and their interpretation using collective and shell model approaches.

Abstract:

A new method is introduced designed to facilitate study of matrix elements in complex β-decay through the measurement of asymmetric β-emission from a low-temperature polarised source. The method involves coincident detection of the β-emission with subsequent γ-transitions to tag the β-spectrum component. The method is demonstrated by application to the decay of 140La.

Abstract:

Shell-model and deformed Hartree-Fock plus BCS calculations are reported for even-even nuclei 18-30O, 18-36Ne, and 20-42Mg; shell-model calculations additionally included 38,40Ne and 44,46,48Mg. Ground-state binding energies and 2+1 quadrupole moments are calculated by both models. Shell-model calculations, aided by a new truncation method, include 2+1 excitation energies and magnetic moments. Hartree-Fock calculations with SkI6, RATP, Z*σ, and SkX Skyrme forces include ground-state deformations and rms radii; SkI6 gives the best overall agreement with experiment. The two models are compared with each other and with experiment. Two-neutron separation energies, evidence for a neutron halo or skin in heavy O isotopes, and deformation of Ne and Mg isotopes are discussed. Both models indicate disappearance of the shell gap at N = 28 (Mg), and the shell model does so additionally at N = 20 (Ne and Mg).

Abstract:

Recent on-line nuclear orientation measurements of nuclear magnetic dipole moments by the method of NMR on oriented nuclei (NMR/ON) have yielded significant new odd-A moments. These include those closest to double magic Sn-132, namely, Sb-133 [Sn-132 plus one g(7/2+) proton] and Te-133(m) [Sn-132 with a pair of g(7/2+) protons and one hole in the h(11/2)- neutron sub-shell]. These close-to-double-magic results allow stringent tests of nuclear moment theory including, as main contributions to deviations from the simple free nucleon (Schmidt limit) values, configuration mixing in the nuclear wavefunction and mesonic exchange current modification to the dipole moment operator. Comparison with theoretical prediction, using established approaches to both these corrections, is discussed showing success in medium mass nuclei comparable to results previously established in light [to Ca-40] and heavy [near Pb-208] nuclei.

Abstract:

Recent on-line nuclear orientation measurements of odd-A nuclear magnetic dipole moments of odd-A Sb, Te and I isotopes by the method of NMR on oriented nuclei mean that we now have complete series of odd-A moments up to, and including, those closest to the double shell closure at Sn-132. In this paper we consider the systematic changes in the measured moments as a function of proton number for the isotonic sequence Sb-133 [g(7/2+)](1) -La-139 [g(7/2+)](7) and as a function of neutron number for the isotopic sequences Sb125-133 and I127-135 and their interpretation using collective and shell model approaches.