I. S. Grant

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.

E0 transitions in the mid-shell even-even Xe nuclides: Decay of 31-s124Cs to levels of124Xe

The results of measurement of the gamma-ray and conversion-electron singles and coincidence spectra from the decay of 31-s124Cs to levels of124Xe are reported. Previously unobserved E0 transitions are identified and the X factors associated with their decay deduced. These results are discussed along with results of measurements on the structure of adjacent Xe nuclides

Deformation in the light Br isotopes

The nuclear ground state spins of the odd-A Br nuclides75, 77, 79Br with Z=35 are all 3/2−. Nilsson orbital calculations show that the 35th proton occupies the f5/2 [301]3/2− orbital for ε<0.20 and the p3/2 [312]3/2− orbital at larger deformations. The magnetic moments of these two states differ by a factor of two, giving clear evidence for the magnitude of the ground state deformation. Low Temperature Nuclear Orientation measurements made in Oxford and Bonn on76, 77gBrFe prepared at ISOLDE, and on line at the SERC Daresbury Laboratory on72, 74m, 75BrFe, have yielded the magnetic moments of these isotopes, using a two non-zero field model with magnetic hyperfine fields of +81.38(6) T and 26(2) T. The spin of the73Br ground state is also deduced. An interpretation of the ground state configurations of these isotopes is given.

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.

On-line nuclear orientation of the deformed neutron-deficient Eu, Sm and Pm isotopes

Low-temperature nuclear orientation measurements made on-line at the SERC Daresbury Laboratory on142mEu,141mSm, and141Pm, with known magnetic dipole moments, have yielded the magnitude of the hyperfine fields of these isotopes in an iron host lattice. Thus measurements for the isotopes139, 138Eu,139mSm, and138Pm yielded values for the respective magnetic moments. Limits on the thermal relaxation times of Eu and Sm isotopes in Fe were also deduced. The results for138Eu appear to contradict the earlier πh11/2⊗νh11/2 ground-state configuration assignment.

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.