Transient-field strength measurements for52Cr traversing Fe hosts at high velocity and polarization transfer mechanisms

Transient-field strengths were measured for⁵²Cr ions traversing polarized Fe hosts at velocities up to 12υ₀ (12υ₀ =c/137 = Bohr velocity). The results are compared with predictions of various transient-field parametrizations and discussed in terms of possible mechanisms by which polarization might be transferred from the Fe host to inner vacancies of the moving Cr ions. Theg-factor of the first 2⁺ state of⁵²Cr was also measured by the transient-field technique and found to be in accord with shell model calculations.     

Gyromagnetic ratios of low-lying rotational states in156, 158, 160Gd

Transient-field precessions were measured simultaneously for levels in the ground-state bands of^{156, 158, 160}Gd as ions of these nuclei traversed a thin polarized Fe foil. Relative g-factors of levels up to 6 ₁ ⁺ were deduced, those of the 4 ₁ ⁺ levels being determined with greatest precision. In contrast with the conclusions of the recent report by Alzner et al. [1], our results are consistent with g(4 ₁ ⁺ ) having the same value in all three isotopes and imply g(2 ₁ ⁺ )=g(4 ₁ ⁺ ) in¹⁵⁶Gd, consistent with nuclear structure models.     

Observation of a superdeformed band in <Superscript>190</Superscript>Pb

A superdeformed band has been observed in the N = 108 isotope ¹⁹⁰Pb. This is the most neutron-deficient Pb isotope in which superdeformed states have been observed. Several theoretical approaches have predicted that N = 108 will mark the limit of observable superdeformation in the Pb isotopes. The band, which consists of five (possibly six) transitions, is observed to feed at least one isomeric level in its decay to the ground state. This decay pattern supports a spin assignment of 10 for the lowest observed level.     

Limit to high-spin isomeric fission

The possibility that high-spin isomers in heavy nuclei might undergo fission has been investigated experimentally. The partial fission lifetime of the 34 μs, I = 34 isomer in ²¹²Fr is found to be at least one hour.     

High-spin g factors and proton alignment in Pt

The average g factors of high-spin states in ^180,182,184Pt were measured by the transient-field technique. In all three isotopes the quasicontinuum g factor at an angular momentum of 20 is g0.37. This contrasts with similar measurements on other nuclei that have 70Z80, where typical values of g0.22 have been attributed to the influence of quasineutron alignments. Evidently proton and neutron configurations are about equally important at high spin in the Pt isotopes near mid-shell. This inference is consistent with the discrete spectroscopy, including the contention, supported by g_K−g_R values, that h_9/2 proton pairs align along with the i_13/2 neutrons at rotational frequencies of ω≈0.3 MeV in ¹⁸⁴Pt. Links between the quasicontinuum g factors and features in the discrete spectroscopy are explored by comparing and contrasting the behavior of ¹⁸⁴Pt and ¹⁶⁶Hf.     

Three- and five-quasiparticle isomers,rotational bands and residual interactions in 175Hf

Two 3-quasiparticle isomers with spins, parities and half-lives of $\text{19}\text{2}$⁺, 1.1 μs and $\text{23}\text{2}$^?, 1.2 ns have been identified at 1433 and 1766 keV in ¹⁷⁵Hf. A third isomer, possibly $\text{35}\text{2}$^? with a 1.2 μs half-life, is found at 3015 keV. The first two are characterised as a $\text{7}\text{2}$⁺ [633] neutron coupled to the known 6⁺ and 8^? 2-proton isomers of the core nuclei. Rotational bands based on the 3-qp isomers are highly perturbed, due to Coriolis mixing, and their structure is reproduced in a band mixing calculation. The energy depression of the 3-quasiparticle states relative to the 2-quasiproton core states is attributed mainly to the residual proton-neutron interaction, and possibly also to blocking effects through neutron admixtures.     

High-spin states and two-quasiparticle structure in 172Hf

Five rotational bands in ¹⁷²Hf have been observed to high spin following the ¹⁶⁰Gd(¹⁶O, 4n)¹⁷²Hf reaction, using γ-γ coincidence techniques. The ground-state band is extended to spin 20⁺ without backbending, in contrast to the neighbouring even-even isotones. The most strongly populated side-band, consisting of separated odd-spin and even-spin sequences, appears to result from the partial decoupling of an i_{$\text{13}\text{2}$} neutron. Three other bands are identified with the following band-heads: an 8^? state at 2006 keV with 163 ns half-life; a 6⁺ state at 1685 keV with a half-life < 16 ns; and a level at 1857 keV with spin 4, 5, 6 or 7 and a half-life < 16 ns. The differences between the bands are discussed in terms of the influence of Coriolis forces and the two-quasiparticle level structure.