R. A. Gatenby

Particle-hole and vibrational states in doubly closed subshell 96Zr from in-beam inelastic neutron and proton scattering

Abstract Through in-beam (n, n′ γ) and (p, p′ γ) reaction studies, we have identified 33 levels in 96 Zr and, from (n, n′) cross section and γ-ray angular distribution data, we have made spin-parity assignments for twenty of these levels. Recent DSAM nuclear level lifetimes were combined with electronic timing measurements in interpreting these states. The 1750 keV 2 + and 2439 keV 3 + states are suggested as the lowest neutron particle-hole multiplet, of ν(3 s 1 2 , 2 d 5 2 − ) type, expected from the double closed subshell picture. On the other hand, the band built on the 1582 keV 0 + shape isomer is determined to have vibrational collectivity up to the two-phonon level. Candidates for two-phonon vibrational states of quadrupole-octupole and double octupole type, associated with the ground-state structure exhibiting octupole softness, are proposed.

Level scheme and mixed-symmetry states of 134Ba from in-beam (n, n′γ) measurements

Abstract The decay properties of the existed states of 134 Ba below 3 MeV have been studied with the (n, n′γ) reaction. From γ-ray excitation function and angular distribution measurements, several new levels, spin-parity values and multipole mixing ratios were obtained. Lifetimes were measured by the Doppler-shift attenuation method, and reduced transition probabilities were calculated for a number of levels using the proton-neutron interacting boson model. The 2029 and 2088 keV states appear to share the properties of the lowest mixed-symmetry 2 + state.

Doppler-shift lifetime measurements in 96Zr with the inelastic neutron scattering reaction

Abstract Lifetimes of states in 96 Zr have been extracted from the Doppler shifts of γ-rays produced by inelastic scattering of accelerator-produced neutrons at incident energies of 3.8 and 4.3 MeV. From these data and the assumption that the Blaugrund theory is applicable, sixteen lifetimes and another seven lifetime limits were determined. Special features of these types of measurements are discussed. For several levels that decay directly to the ground state, spin assignments have been deduced from the γ-ray angular distributions. From measured B( E 2) and B (E1) values, support is found for suggested collective quadrupole and octupole structures in this nucleus.

Two-phonon character of the lowest J pi =1(-) state of 142Nd.

The decay properties of the 3424-keV 1{sup {minus}} state in {sup 142}Nd, which has long been interpreted as a member of the quadrupole-octupole two-phonon quintet, and of the lowest 3{sup {minus}} state, the octupole phonon, have been examined with the ({ital n},{ital n}{prime}{gamma}) reaction. {gamma}-ray branching ratios of these states have been determined, and level lifetimes have been measured by the Doppler-shift attenuation method. These data provide strong support for interpreting the 1{sup {minus}} state as having a significant two-phonon 2{sup +}{direct_product}3{sup {minus}} component.

Two-phonon character of the lowest {ital J}{sup {pi}}=1{sup {minus}} state of {sup 142}Nd

The decay properties of the 3424-keV 1{sup {minus}} state in {sup 142}Nd, which has long been interpreted as a member of the quadrupole-octupole two-phonon quintet, and of the lowest 3{sup {minus}} state, the octupole phonon, have been examined with the ({ital n},{ital n}{prime}{gamma}) reaction. {gamma}-ray branching ratios of these states have been determined, and level lifetimes have been measured by the Doppler-shift attenuation method. These data provide strong support for interpreting the 1{sup {minus}} state as having a significant two-phonon 2{sup +}{direct_product}3{sup {minus}} component.

Two-phonon character of the lowestJπ=1−state ofNd142

The decay properties of the 3424-keV 1{sup {minus}} state in {sup 142}Nd, which has long been interpreted as a member of the quadrupole-octupole two-phonon quintet, and of the lowest 3{sup {minus}} state, the octupole phonon, have been examined with the ({ital n},{ital n}{prime}{gamma}) reaction. {gamma}-ray branching ratios of these states have been determined, and level lifetimes have been measured by the Doppler-shift attenuation method. These data provide strong support for interpreting the 1{sup {minus}} state as having a significant two-phonon 2{sup +}{direct_product}3{sup {minus}} component.

Doppler Shift Lifetime Measurements at Low Recoil Velocities and Mixed‐Symmetry States in 134Ba

It is shown that the low recoil energy DSAM provides reliable lifetimes in heavy nuclei. By applying the (n,n’γ) reaction combined with DSAM to 134Ba, a great amount of new information was obtained, including level lifetimes of two mixed‐symmetry 2+ states. These data are compared with IBM‐2 calculations.

Search for various collective excitation modes with the (n, n’γ) reaction

It is demonstrated that combination of the (n,n’γ) reaction and the Doppler Shift Attenuation Method is an extremely useful tool to identify various kinds of low energy collective excitations. Evidences for double octupole and quadrupole-octupole modes are presented in96Zr and144Sm nuclei. Newly measured transition rates of the 2+ mixed-symmetry states in the134Ba O(6) nucleus are reported.

Evidence for Octupole-Octupole and Quadrupole-Octupole Excitations in Spherical Nuclei

The nuclei 96Zr and 144Sm have been studied with the (n,n ’γ) reaction, and lifetimes of many states have been extracted from the observed doppler shifts of the deexciting γ rays. A large number of fast El transitions have been observed, and the identification of possible members of the octupole-octupole and quadrupole-octupole multiplets in these nuclei has been made.

Doppler-Shift Lifetime Measurements in 96Zr

While differing types of collective structures have been proposed [1–3] in 96Zr, γ-ray transition rates in this nucleus were not known. To assess the degree of collectivity of excited states of 96Zr, we have measured the Doppler shifts of γ rays emitted following inelastic neutron scattering (INS) of monoenergetic accelerator-produced neutrons and determined lifetimes of many levels of this doubly closed subshell nucleus.