P. Kleinheinz

Particle hole yrast states in146Gd and147Gd and the Z=64 shell closure

The level structures of146Gd and147Gd have been investigated by in-beamγ-ray ande− spectroscopy with (α, xn) reactions on enriched Sm targets. Detailed level schemes up to ∼4 MeV, which differ radically from earlier schemes, are reported. The energy levels are characterized as particle-hole excitations using empirical single particle energies and two nucleon interactions. Analysis of pure 1p 1h proton excitations demonstrates that theZ=64 andN=82 energy gaps are about equally large.

Particle plus octupoleM2/E3 isomers and high-spin particle-hole states in147Tb and148Tb

The level structures of theN=82 andN=83 nuclei147Tb and148Tb have been studied by means of (α, 8n) and (α,7n) reactions induced by 68 to 110 MeVα particle bombardments of151Eu targets. In-beam conversion electron measurements have established that isomers withT1/2=4.8(6)ns in147Tb andT1/2=22(1)ns in148Tb decay byM2+E3 transitions to the ground states. The measuredB(E3) values show that the isomeric states arise from the coupling of the valence nucleon(s) to the146Gd core octupole. Particlephonon coupling in these nuclei and in the one-neutron nucleus147Gd is discussed and compared with well known cases involving the208Pb core. The higher lying yrast states in the two Tb nuclei are described as shell-model particle-hole excitations using empirical single particle energies and nucleon-nucleon interactions.

The 3− state in the doubly closed shell nucleus 64 146 Gd82

Inbeam γ-ray angular distribution measurements establishIπ = 3− for the 1579 keV first excited state in146Gd.

Properties of the 3− first excited state in the doubly closed shell nucleus146Gd

Conversion electron measurements confirm the 3− assignment recently proposed for the 1579 keV first excited state in146Gd. Fromγγ- ande−γ-coincidence data the half life of that state has been determined asT1/2=1.06±0.12 ns.

Prolate and oblate 10+ isomers in 140Sm78 and 142Gd78

Abstract The N = 78 isotones 140Sm and 142Gd have been studied with α-particle- and HI-induced reactions. In both nuclei two close-lying 10+ isomers at ∼ 3.2 MeV have been established, and from the feeding E2 cascades they are characterized as the prolate ν h 11 2 −2 and the oblate π h 11 2 2 excitations. A third E2 cascade feeding into the 142Gd 8+ state is interpreted as the continuation of the collective ground state sequence that might assume the properties of a perfect deformed rotor for spins above 10.

Particle-octupole coupling in N=83 nuclei from neutron transfer studies with polarized deuterons☆

Abstract Neutron pick-up measurements have identified the s 1 2 and d 3 2 holes states in 147 Gd, 145 Sm, and 143 Nd. The results also locate the 1 2 + and 3 2 + members of the v f 7 2 ×3 − septuplet via their admixtures from these hole states. Additional energy perturbations of the septuplet result largely from a negative quadrupole moment of the octupole phonon, with a Z -dependence consistent with the microscopic structure of the 3 − excitation in the N =82 nuclei.

Multiparticle- and particle x octupole states in 65 149 Tb84

Yrast- and above-yrast states in149Tb were investigated in (α, 6n) and (7Li, 2n) in-beamγ-ray experiments. The yrastγ-ray cascade strongly populates three-valenceparticle states involving theh11/2 proton and thef7/2,h9/2, or;i13/2 neutron orbitals, as well as the high-spin levels formed by the couplings of the three149Tb valence particles, to the low-lying146Gd octupole phonon and to higher-lying proton particle-hole core excitations. The data give the (πh11/2vi13/2)12− attraction free of octupole contributions as -631 keV. The shell model with empirical two-particle- and particle-phonon residual interactions gives an excellent quantitative description of the149Tb energy levels. It is noted that the observed highspin members of theπh11/2vh9/2vf7/2 configuration closely resemble the lowest symmetric and mixed-symmetry representations of theS3 permutation group.

The 235 μs 9+ isomer in 63 146 Eu83

Through (p,2n) in-beam γ and e− measurements the excitation of the 235 μs 9+ isomer in146Eu has been determined to be 666.3 keV. High spin members of the πd52/−1 νf7/2 and πg72/−1 νf7/2 particle hole multiplets populated in the isomeric decay were located.

β+-endpoint measurements near100Sn and146Gd

With a summation-free β+-endpoint spectrometer the β+-decay energies of104Sn,147Tb,148, 149Dy,149Ho,150Er, and151Tm were remeasured with improved accuracy. Combined with known proton and alpha decay energies, the resulting QEC values lead to atomic masses of very neutron-deficient isotopes including nuclei beyond the proton drip-line such as109I and113Cs. Furthermore, the Gamow-Tellerβ-strength of the even-even nuclei104Sn,148Dy, and150Er is reevaluated with reduced uncertainty.

Shell model yrast states in theN=79 nuclei141Sm and143Gd

In (α,5n) in-beam γ- and electron measurements we have established high-spin states in the 3-neutronhole nuclei141Sm and143Gd. Observed energy levels below 4 MeV are interpreted in terms of shell model configurations where the odd h11/2 neutron hole couples to the N=80 core excitations containing one h11/2 proton particle or one h11/2 neutron hole. Higher-lying yrast states are built on a 23/2− level at Rd 3.2 MeV probably involving the πh12/2guh112/−1 configUTa-tion.