Non-yrast States Research Articles

Complete Particle-Core Multiplets Populated inRu99by the (He3,2nγ) Reaction

Extensive sets of yrast and nonyrast states in /sup 99/Ru have been populated by the reaction /sup 98/Mo(/sup 3/He,2n..gamma..)/sup 99/Ru. The population of nonyrast states is attributable to the characteristics of the reaction rather than the specifics of the nuclear structure involved. Several complete particle-core multiplets have been successfully interpreted with a particle-rotor model.

High-spin yrast and non-yrast bands in 176Os, 178Os and 180Os

High-spin yrast and non-yrast states have been identified in 176Os, 178Os and 180Os using ( 16 O, xn) reactions, and γ-ray techniques. Band crossing anomalies are observed in each of the positive-parity yrast bands. The magnitude of these anomalies decreases with decreasing neutron number, an effect attributed to the change in the moment of inertia of the ground state rotational bands. A 23 ns isomer, predominantly K π = 7 −, is identified at 1930 keV in 180Os. The configuration of this isomer is discussed on the basis of the properties of its rotational band. Negative parity, odd and even spin, sideband sequences are observed in each isotope. Their relationship to rotation-aligned octupole and 2-quasiparticle bands is discussed from their excitation energies, band spacings, and decay properties. Detailed calculations for Coriolis mixed bands are carried out for the likely 2-quasiproton and 2-quasineutron configurations. An anomaly observed at spin 17 in the odd-spin negative-parity sequence in 180Os is attributed to a band crossing with a fourquasiparticle configuration.

Medium-spin levels and the character of the 20.4 ns [formula omitted] isomer in 145Gd

Levels of the N = 81 nucleus 145Gd have been investigated by in-beam γ-ray and conversion electron spectroscopy with the 144Sm( 3He, 2n) reaction. Fourteen new low- and medium-spin states between 1.0 and 2.4 MeV excitation, the known yrast levels up to spin 21 2 + , five other high-spin non-yrast states and a new 20.4 ns 13 2 isomer at 2200.2 keV in 145Gd have been observed. The isomer decays via a fast 927.3 keV E3 transition with B(E3) = 48 ± 7 W.u. Another weaker decay branch is a mixed, strongly hindered E1 + M2 + E3 transition to the v h −1 11 2 state. We propose an octupole v f 7 2 j −2 × 3 − main configuration for the isomer, analogous to the 997 keV 13 2 + isomer in 147Gd. The levels of 145Gd are discussed on the basis of the spherical shell model.

The Limits of Studying High-Spin States by Discrete-Line Gamma-Ray Spectroscopy

Recent (HI, xn) data on rotational Yb and Hf nuclei are used to describe the motivations and techniques for pushing discrete-line spectroscopy to the realm of the weakly populated yrast and non-yrast states. Three aspects of these studies are discussed: extraction of moments of inertia in different aligned bands, observation and understanding of high-frequency band crossings, and dependence of feeding patterns on nuclear structure.

Non-yrast states inPd101and their rotational interpretation

Several non-yrast states of both parities in $^{101}\mathrm{Pd}$ have been observed using three-detector $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence measurements following the reaction $^{92}\mathrm{Zr}(^{12}\mathrm{C}, 3n)^{101}\mathrm{Pd}$. Energy levels, $\ensuremath{\gamma}$-ray mixing ratios, and branching ratios are deduced from the data and compared with the results of a rotational model calculation. Five of the newly discovered states are identified as non-yrast members of rotational bands based on the $\frac{5}{{2}^{+}}$ and $\frac{11}{{2}^{\ensuremath{-}}}$ states.NUCLEAR STRUCTURE $^{92}\mathrm{Zr}(^{12}\mathrm{C}, 3n)^{101}\mathrm{Pd}$ at 48 MeV; measured ${I}_{\ensuremath{\gamma}}(\ensuremath{\theta})$, 3-detector $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coin, $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ DCOQ. $^{101}\mathrm{Pd}$ deduced levels, $J$, $\ensuremath{\pi}$, $\ensuremath{\gamma}$ mixing ratios. Rotational model calculations, Coriolis, recoil, calculated levels, mixing ratios, branching ratios, half-lives.

Theoretical rotational signatures for neutron pickup reactions to [formula omitted] bands

It is shown with the particle-rotor model that non-yrast low-spin states, which are structurally related to the rotation-aligned ( i 13 2 ) 2 band causing backbending at higher spins, can be populated selectively by means of l=6 neutron pickup from an odd-neutron target with an appropriate ground-state configuration.