Yu Hu Zhang

High-spin isomer and level structure of 145Sm

Abstract High-spin states of 145 Sm were studied by using the reactions 20 Ne( 136 Xe,α7n), 16 O( 136 Xe,7n), 139 La( 10 B,4n) and 138 Ba( 13 C,6n). The level scheme was extended up to the state at 14.6 MeV. The excitation energy and the spin-parity of the 0.96 μs high-spin isomer were determined to be 8.8 MeV and ( 49 2 + ), respectively. Experimental results were discussed comparing with the deformed independent particle model calculation. High-spin isomers observed in N = 83 isotones were interpreted to be caused by the sudden shape change from near spherical to oblate. The Z = 64 shell gap energy was found to decrease from 2.4 to 2.0 MeV as the proton number decreases from Z = 64 to 61.

High-spin isomeric state in144Pm

A new high-spin isomeric state with a half-life of ≥2μs was found in144Pm by observing the14N(136Xe,6n)144Pm reactions. The excitation energy and spin of the isomer were estimated to be ∼7.4 MeV and ∼27+, respectively. Filling gas in a recoil ion separator was used as the target material.

Observation of isomeric states in197Bi

The high-spin states in197Bi have been studied with the187Re(16O, 6n)197Bi reaction at16O energies between 85 and 105 MeV. In-beam measurements ofγ-ray excitation functions,γ-γ-t coincidences and γray angular distributions were carried out with 6 BGO(AC) HPGe detectors and one intrinsic Ge planar detector. 11 new transitions and 3 new isomers at 2089, 2357 and 1968+Δ keV with t1/2 =19.3±4.9, 53.4±20.5 and 18.0±3.1 ns., respectively, were observed, and a level scheme is established. Some differences between the present work and the previous results were found.

High-spin states of145Sm

High-spin states of145Sm were studied by using the20Ne(136Xe, α7n),139La (10B, 4n) and138Ba(13C,6n) reactions. The decay scheme of a high-spin isomer of145Sm was established. The excitation energy and the spin-parity of the isomer were determined to be 8.8 MeV and (49/2+), respectively. The level scheme was extended up to the (65/2) state at 14.6 MeV. The experimental results were discussed comparing with the deformed independent particle model (DIPM) calculation.

Search for positive parity bands in 117Xe

Abstract Excited states of 117 Xe were populated via the reaction 28 Si + 92 Mo at 100–120 MeV. More than 40 new γ-transitions and three new positive parity bands have been obverved by means of in-beam γ-ray spectroscopy. The previously known ν h 11 2 bands were confirmed, and the ν g 7 2 favored band was extended up to 47 2 + in which two bandcrossings have been observed at h ω =0.33 and 0.44 MeV, respectively. The band structures have been discussed by means of TRS and CSM calculations. A newly observed rotational band consisting of five γ-transitions has been considered as the π h 11 2 band of 117 Cs.

Observation of high spin states in117Xe

High spin states of117Xe have been investigated by means of in-beam γ-ray spectroscopy using the reaction92Mo(28Si, 2pn) at beam energies of 100 to 120 MeV. The previously known νh11/2 bands are confirmed and the νg7/2 favored-signature band is extended up to 47/2+, in which two band crossings are observed at ħω=0.33 and 0.44 MeV, respectively. Two new positive-parity bands have been established, one of which is most likely the νg7/2 unfavored-signature band. A new transition cascade with irregular level spacings is also observed.