R.R. Chasman

Superdeformation near A = 190☆

Abstract Calculations have been carried out in the cranked Strutinsky method, using a Woods-Saxon potential for protons and neutrons, for nuclides near A = 190. Many nuclides are found to be superdeformed. The depth of the superdeformed minimum, its excitation relative to the normal minimum and moments of inertia of superdeformed bands in this mass region are presented. Deformation parameters and single particle energy level differences at the Fermi level are tabulated for several nuclides of interest.

N-P pairing in nuclei.

Variational wavefunctions for treating N-P pairing in the T=1 and T=0 channels are presented. Alpha-like correlations are explicitly included in the wavefunctions and arbitrary single-particle energy level spacings are allowed. A triple projection before variation procedure is used to obtain these wavefunctions. Taking a model system with equally spaced single-particle levels, several features of nuclei near the N=Z line are calculated. A new type of multiple degeneracy is found in nuclei near the N=Z line.

Superdeformed and hyperdeformed banana shaped nuclides near A = 190

Abstract The effects of Y 1 3 ( θ , φ ) deformations on the energy surface of nuclides in the A = 190 region has been studied. Many nuclides with superdeformed and hyperdeformed minima have been found. The states associated with these minima are found to be near yrast at I = 40.

A superdeformed band in 151Dy

Abstract A rotational band of 19 (possibly 20) transitions extending to spin ∼ 131 2 h has been observed in 151Dy with an average dynamic moment of inertia I (2) = 79 h 2 MeV −1 . This band is identified as a superdeformed band in 151Dy. The value of I (2) agrees with cranked Strutinsky calculations. Similarities as well as striking differences with the superdeformed bands of neighboring nuclei are observed.

The effects of pairing on superdeformed rotational bands near A=190

Abstract The second moments of inertia of superdeformed bands in several Hg and Tl isotopes are analyzed. The roles of pairing forces, 2 6 -pole deformation and nuclear radius parameters on these moments of inertia are treated.

Persistence of deformed shapes in the neutron-deficient Pb region

Abstract Calculations are presented for low-lying 0 + excited states in the neutron deficient Pb isotopes 182–190 Pb using both the HFB method with a Gogny interaction and a many-body method with phenomenological interaction strengths. The calculations suggest the presence of an as yet unobserved oblate 0 + state in 184 Pb.

Level structure of 225Ac

Abstract The level scheme of 225 Ac has been deduced from the study of the α-decay of 229 Pa and β − decay of 225 Ra. Sources of 229 Pa were produced by the 229 Th(d, 2n) and 230 Th(d, 3n) reactions, and the 225 Ra activity was obtained by milking a 229 Th sample. Gamma singles spectra of 229 Pa and 225 Ra were measured with high-resolution Ge detectors placed in a very low background shield. Alpha-gamma and γγ-coincidence measurements were made with 229 Pa sources. Using the ratio of the KX-ray and γ-ray intensities obtained from gated γ-ray spectra, we were able to deduce K conversion coefficients of the 115.55 and 120.80 keV transitions which gave M1 multipolarities for these transitions. Four bands were identified: K π = 3 2 − , ground; 3 2 + , 40.09 keV; 5 2 − , 120.80 keV; and 5 2 + , 155.65 keV. The half-life and alpha branching ratio, α/(α+EC), were measured to be 1.50 ± 0.05 d, and (0.48±0.05)%, respectively.

Discrete and continuum Gamma-ray studies of 147Gd and 148Gd

Abstract Discrete and continuum γ-ray studies of the N = 83, 84 nuclei 147 Gd and 148 Gd have been performed using ( 36 S, 5n) and ( 36 S, 4n) reactions on 116 Cd. The level schemes of both nuclei have been extended to excitation energies above 18.5 MeV, with assigned spins up to 83 2 in 147 Gd and up to 46 in 148 Gd. Evidence for a change in character along the yrast line from single particle to collective was found at the highest spins in 148 Gd, but not in 147 Gd. For 148 Gd a study of γγ correlation matrices revealed a ridge-valley structure with a ridge spacing indicative of superdeformation. No evidence for a similar structure in 147 Gd was found.

Odd-multipole correlations in the light actinides☆

Abstract The role of a 2 5 -pole particle-hole interaction in the light actinides is studied with many-body wave functions capable of accommodating many single-particle levels. The wave functions are described. Properties of ground and excited states in several light actinides are discussed.

Neutron single particle states above the N=152 subshell☆

Abstract Single-particle states above the N=152 subshell have been studied by high-resolution 250Cf(d,p) reaction. All states between the 152 and 164 neutron subshell have been identified. A tentative assignment has been made for the 1 2 −[761] orbital.