Y. X. Guo

Low-spin signature inversion in the {pi}h{sub 9/2}x{nu}i{sub 13/2} oblate band of {sup 190}Tl

High-spin states in {sup 190}Tl have been studied experimentally by using the {sup 160}Gd({sup 35}Cl,5n) fusion-evaporation reaction at beam energies of 167 and 175 MeV. A rotational band built on the {pi}h{sub 9/2}x{nu}i{sub 13/2} configuration with oblate deformation has been established for {sup 190}Tl. Spin values are assigned by adopting the results from {alpha}-{gamma} decay work for {sup 194}Bi found in the literature. With the configuration and spin-parity assignments, the low-spin signature inversion has been revealed for the {pi}h{sub 9/2}x{nu}i{sub 13/2} oblate band in {sup 190}Tl. It is the first experimental observation of low-spin signature inversion for a band associated with the oblate {pi}h{sub 9/2}x{nu}i{sub 13/2} configuration. The low-spin signature inversion for the oblate {pi}h{sub 9/2}x{nu}i{sub 13/2} band can be interpreted by the two-quasiparticle-plus-rotor model including a J-dependent p-n residual interaction.High-spin states in Tl-190 have been studied experimentally by using the Gd-160(Cl-35,5n) fusion-evaporation reaction at beam energies of 167 and 175 MeV. A rotational band built on the pi h(9/2)circle times nu i(13/2) configuration with oblate deformation has been established for Tl-190. Spin values are assigned by adopting the results from alpha-gamma decay work for Bi-194 found in the literature. With the configuration and spin-parity assignments, the low-spin signature inversion has been revealed for the pi h(9/2)circle times nu i(13/2) oblate band in Tl-190. It is the first experimental observation of low-spin signature inversion for a band associated with the oblate pi h(9/2)circle times nu i(13/2) configuration. The low-spin signature inversion for the oblate pi h(9/2)circle times nu i(13/2) band can be interpreted by the two-quasiparticle-plus-rotor model including a J-dependent p-n residual interaction.

Characteristics of a CsI(Tl) Compton-suppressed clover detector

The performance of a four fold segmented clover detector coupled to a CsI-suppressed shield has been tested using several standard radioactive sources. The summing characteristics, hit patterns and absolute efficiency were measured in both crystal and clover modes. Peak-to-total ratios of 57.3% and 45.6% in suppressed clover mode have been determined for 137Cs and 60Co sources, respectively. A Geant4 simulation of the suppressed clover detector, including the segmentation of the germanium crystals, has been created, and the simulation results agreed very well with the experimental data.

High-spin states in Au-188: Further evidence for nonaxial shape

The high-spin level structure of {sup 188}Au has been investigated via the {sup 173}Yb({sup 19}F,4n{gamma}) reaction at beam energies of 86 and 90 MeV. The previously reported level scheme has been modified and extended significantly. A new I{sup {pi}}=20{sup +} state associated with {pi}h{sub 11/2}{sup -1} x {nu}i{sub 13/2}{sup -2}h{sub 9/2}{sup -1} configuration and two new rotational bands, one of which is built on the {pi}h{sub 9/2} x {nu}i{sub 13/2} configuration, have been identified. The prolate-to-oblate shape transition through triaxial shape has been proposed to occur around {sup 188}Au for the {pi}h{sub 9/2} x {nu}i{sub 13/2} bands in odd-odd Au isotopes. Evidence for {pi}h{sub 11/2}{sup -1} x {nu}i{sub 13/2}{sup -1} structure of nonaxial shape with {gamma}<-70 deg. has been obtained by comparison with total Routhian surface and cranked-shell-model calculations.

SEARCH FOR SIGNATURE INVERSION IN THE πi13/2 ⊗ νi13/2 BANDS IN 182,184,186Au

Search for low-spin signature inversion in the πi13/2 ⊗ νi13/2 bands in odd-odd 182,184,186Au has been conducted through the standard in-beam γ-spectroscopy techniques. The experiments for 182Au and 186Au have been performed in the Japan Atomic Energy Agency (JAEA) via the 152Sm(35Cl,5n)182Au and 172Yb(19F,5n)186Au reactions, respectively. A study of 184Au has been made using a multi-detector array GASP in LNL, Italy, via the 159Tb(29Si,4n)184Au reaction. The πi13/2 ⊗ νi13/2 bands in these three nuclei have been identified and extended up to high-spin states. In particular, the inter-band connection between the πi13/2 ⊗ νi13/2 band and the ground-state band in 184Au has been established, leading to a firm spin-and-parity assignment for the πi13/2 ⊗ νi13/2 band. The low-spin signature inversion is found in the πi13/2 ⊗ νi13/2 bands in 182,184,186Au according to our spin-assignment and the signature crossing observed at high-spin states.

High-spin level scheme and decay of the 67-{mu}s isomer in {sup 142}Pm

Excited states in Pm-142 are investigated via the Te-128(F-19, 5n) Pm-142 reaction at beam energies from 75 to 95 Me V by using techniques of in-beam gamma-ray spectroscopy. Measurements of gamma-ray excitation function, X-gamma and gamma-gamma-t coincidences are performed with 10 BGO(AC)HPGe detectors. Decay of the previously known 67-mus isomer in Pm-142 is observed and added into the new level scheme. This isomer is definitely placed at the excitation energy of 2828.5keV. The spin of this isomer is suggested to be 13h according to the measured gamma-ray anisotropies.

Properties of the rotational bands in {sup 161}Er

High-spin states in {sup 161}Er have been studied experimentally using the {sup 150}Nd({sup 16}O,5n) reaction at a beam energy of 86 MeV. The 5/2{sup +}[642], 3/2{sup -}[521], and 11/2{sup -}[505] bands are extended up to high-spin states, and particularly the {alpha}=-1/2 branch of the ground state 3/2{sup -}[521] band is revised significantly. The relatively enhanced E1 transitions from the 3/2{sup -}[521] band to the 5/2{sup +}[642] band are observed. The band properties are analyzed within the framework of a triaxial particle-rotor model, and near-prolate shape and triaxial deformation are proposed to the 3/2{sup -}[521] and 5/2{sup +}[642] bands, respectively. Signature inversion occurs in the 3/2{sup -}[521] band after the band crossing in {sup 161}Er, and the systematics of the signature inversion associated with the 3/2{sup -}[521] configuration are discussed. By analyzing the properties of the relatively enhanced E1 transitions, it is found that the R(E1/E2) values show angular momentum dependence before the band crossing, and these enhanced E1 transitions could be attributed to octupole softness.

Properties of the {pi}h{sub 11/2} band in the stable nucleus {sup 193}Ir

Excited states in the stable nucleus {sup 193}Ir have been investigated through an in-beam {gamma}-ray spectroscopic technique following the {sup 192}Os({sup 7}Li, {alpha}2n) reaction at a beam energy of 44 MeV. A level scheme built on the {pi}h{sub 11/2} isomer has been extended to high-spin states using eleven newly observed {gamma} transitions. The {pi}h{sub 11/2} band is proposed to be formed by coupling an h{sub 11/2} proton to a core with large triaxial deformation. Three-quasiparticle states are suggested in {sup 193}Ir on referring to the similar states in {sup 187}Ir. The features of signature splitting in the {pi}h{sub 11/2} bands of {sup 187-193}Ir are discussed with the help of total Routhian surface calculations.

First observation of low-spin signature inversion in the πh9/2 ⊗ vi13/2 oblate band

Excited states in 190 Tl have been studied experimentally using the 160 Gd( 35 Cl, 5n) reaction, and resulted in the identification of a strongly coupled band based on the πh 9/2 ⊗ vi 13/2 configuration with oblate deformation. Combining with the results from the previous α-decay of 194 Bi, spin values have been proposed for the πh 9/2 ⊗ vi 13/2 oblate band in 190 Tl. This oblate band shows low-spin signature inversion. It is the first experimental observation of low-spin signature inversion for a band associated with the oblate πh 9/2 ⊗ vi 13/2 configuration.