V. R. Green

Iodine magnetic moments: Shape coexistence and N = 64 subshell closure

Abstract The magnetic dipole mooments of 117 I, 118 I g , 118 I m , 119 I, 120 I g , 120 I m , 121 I and 122 I have been measured by the technique of on-line low-temperature nuclear orientation. The ground-state moments show the influence of N = 64 subshell closure, with near-spherical configurations, while the moments of the metastable states suggest large prolate deformations.

On-line nuclear orientation of 118I and the identification of the g92 intruder orbital

Abstract The magnetic dipole moments of 118 I g (t 1 2 =12 min ) and 118 I m (t 1 2 = 8 min ) have been measured to be |μ| = 2.4±0.4 nm and 4.7±0.7 nm, respectively, using the technique of non-linear orientation. In order to understand the high moment of the Iπ=(7−) metastable state, it is necessary to invoke the excitation of a g 9 2 proton hole across the Z = 50 shell gap, together with a considerable quadrupole deformation. In the daughter nucleus, 118Te, a low-lying Kπ = 0+ state is established, and the possible influence of shape coexistence is discussed.

γ-ray linear polarization measurement on oriented nuclei

The present status of γ-ray linear polarization measurements on oriented nuclei is discussed. The formalism used in the analysis of experimental data is summarized and complemented by formulae for γ-transitions with triple multipole mixing. A survey of the present technique of detection of γ-ray linear polarization, using Compton polarimeters, is given. Two important applications of γ-ray linear polarization measurements are briefly surveyed, namely, the measurement of theg-factors excited states and the investigation of time-reversal symmetry in atomic nuclei.

IBA-2 model calculation on even mass tellurium isotopes compared with results of recent nuclear orientation experiments

Calculations using the IBA-2 model code are presented for even-even tellurium isotopes118Te to124Te. Three parameter sets are used, two from previous work and a third chosen to give optimum fit to experimental positive parity energy levels and B(E2) ratios. With only two additional parameters, each with simple physical interpretation, the three parameter sets are shown to give excellent fits to the known collective negative parity states in these isotopes. Failure to fit the O2+,O3+ and 23+ levels suggests these may be 4p-2h intruder states, although their Behaviour with varying neutron number is not as clearly characteristic of such configurations as is found for the 2p-4h states in Cd isotopes.

The Daresbury On-Line Isotope Separator (DOLIS)

Abstract The isotope separator DOLIS, which is on-line to the Daresbury Laboratorys 20-MV tandem accelerator, is used to measure nuclear moments and decay schemes. Separated beams may be collected on a tape and transported to a counting station, implanted directly into a host lattice at on-line temperatures down to less than 10 mK, or allowed to interact with a collinear laser beam. The present status of DOLIS and its ancillary equipment is described.

On-line low-temperature nuclear orientation at DOLIS-COLD

Abstract The Daresbury On-Line Isotope Separator-Cryogenic On-Line Device (DOLIS-COLD), consisting of a 3He-4He dilution refrigerator coupled to an on-line isotope separator, has proved to be a powerful system for the study of nuclei far from stability. The design and performance of DOLIS-COLD is discussed. To illustrate the capabilities of the system, examples of magnetic moment measurements by static low-temperature nuclear orientation and by NMR on oriented nuclei (NMR/ON) are presented.

On-line nuclear orientation and relaxation studies of Cs isotopes

The hyperfine field of CsFe has been measured to be (+)40.8(0.7)T, using the technique of on-line low temperature nuclear orientation. The time dependent relaxation of121CsmFe has also been investigated using a new technique, giving a Korringa constant Ck of 0.059 (15) sK. From this, an effective relaxation time of 3.0 (0.8)s can be deduced for the short lived118Csm(T1/2=17s). This value has then been used to extract the magnetic moment of118Csm to be |μ|=5.4 (1.1) nm.

The NMR of 116Sbg cryogenically oriented on-line in iron

Abstract The resonant destruction of gamma-ray anisotropy from 116 Sb g (t 1 2 =16 m , I π =3 + ) has been observed at 161.65 ( MHz, using the technique of NMR/ON. The deduced magnetic moment is |μ|=2.175(9) μ N. The change in the Iπ=3+ magnetic moments between 116Sb and 120Sb can be accounted for by variation inthe odd-neutron contribution, the odd proton in these antimony states behaving as a spectator.

Nuclear orientation and coincidence studies of118I and118Cs isotopes

Gamma-gamma coincidence and on-line nuclear orientation experiments have been done on118Ig(2−),118Im(7−),118Csg(2−) and118Csm(8−). The activities were produced by 175 MeV32,34S beams on93Nb and the products passed through an isotope separator. Nuclear moments for the118I isomers are deduced. The decay scheme of118Te is given and various spin assignments made, particularly 1944.3 KeV (3−) and 957.3 KeV (o+). Equilibrium distortion of the118I ground state is discussed briefly.

Gamma-ray linear polarization measurement on oriented nuclei

Measurement of linear polarization of gamma-rays from nuclei oriented by hyperfine interaction at low temperatures using the3He/4He dilution refrigerator at the SERC Daresbury Laboratory is reported. Three different types of a Compton polarimeter were assembled using coaxial Ge(Li) detectors. The method was applied to192IrFe and60CoFe and a polarization detection efficiency curve and a figure of merit for each polarimeter were produced. As a result of combined directional distribution and linear polarization measurements multipole mixing ratios of several transitions in192Pt have been obtained and are compared with theoretical predictions.