Shuifa Shen

LOW-SPIN STATES OF 83Rb EXCITED IN THE 83Sr(β++EC)83Rb DECAY

Gamma-rays from the 83Sr(β++EC)83Rb decay have been investigated with Compton suppressed HpGe detectors. The activity was produced via the 85Rb(p,3n) reaction at 27.1 MeV beam energy. Singles in multispectra mode and γ–γ coincidence experiments were performed. Approximately 190 transitions including 94 new transitions and 19 new levels were assigned to 83Rb, based on their measured half-life and/or observation in coincidence with well-known lines. A decay scheme has been constructed consisting of 41 excited states and 180 transitions in 83Rb. Additional new information has been obtained on γ-ray branching ratios, log ft values, spins and parities.

Decay of 1.643-hr 95Ru to 95Tc

The decay of 95Ru has been investigated by means of γ-ray spectroscopy. The 95Ru nuclei were produced by the reaction 92Mo(α,n)95Ru at the beam energy of 17 MeV. High-purity Ge detectors have been used singly and in coincidence to study γ-rays in the decay of 95Ru to 95Tc. 132 γ-rays are reported, among them, energies and intensities for 127 transitions have been determined. A decay scheme of 95Ru with 31 levels is proposed which accommodates 127 of these transitions. Spins and parities for three new levels are proposed from calculated logft values, measured γ-ray branching ratios, and in-beam experiment results of the daughter nucleus 95Tc.

Signature splitting inversion and backbending in80Rb

High spin states of 80Rb are studied via the fusion-evaporation reactions 65Cu+19F, 66Zn+18O and 68Zn+16O with the beam energies of 75 MeV, 76 MeV and 80 MeV, respectively. Twenty-three new states with twenty-eight new \gamma transitions were added to the previously proposed level scheme, where the second negative-parity band is significantly pushed up to spins of 22^{-} and 15^{-} and two new sidebands are built on the known first negative-parity band. Two successive band crossings with frequencies 0.51 MeV and 0.61 MeV in the \alpha=0 branch as well as another one in the \alpha=1 branch of the second negative-parity band are observed for the first time. Signature inversions occur in the positive- and first negative-parity bands at the spins of 11\hbar and 15\hbar, respectively. The signature splitting is seen obviously in the second negative-parity band, but the signature inversion is not observed. It is also found that the structure of the two negative-parity bands is similar to that of its isotone ^{82}Y. Signature inversion in the positive-parity yrast band with configuration \pi g_{9/2} \otimes \nu g_{9/2} in this nucleus is discussed using the projected shell model (PSM).

DECAY OF (188)Re AND TRS CALCULATIONS FOR ITS DAUGHTER NUCLIDE (188)Os

The gamma-ray spectra of (188)Re decay have been studied by using Compton-suppressed spectrometer and three parameter gamma-gamma-T list coincidence system. Experiemental data analysis demonstrated that six gamma-rays at 557, 810, 1463, 1867, 1936 and 2022 keV and three levels at 1443, 1936 and 2022 keV are confirmed again. seven new gamma-rays at 309.60 +/- 0.04, 826.90 +/- 0.02, 979.29 +/- 0.08, 1103.7 +/- 0.4, 1828.2 +/- 0.1, 1842.5 +/- 0.2 and 1982.5 keV are assigned. the beta(-) decay branching ratio is deduced. In addition, in order to study this gamma-unstable nucleus, shape calculations using the Hartree-Fock-Bogoliubov-like formalism were carried out for positive-parity states in (188)Os. The TRS plots reveal that, as the spin increases up the band, the triaxiality parameter gamma changes.

Signature inversion caused by shape change in 84Rb

The angular momentum projected shell model (PSM) is applied to the nucleus Rb-84. The results of theoretical calculations about the positive-parity yrast band with configuration pig(9/2) circle times nu(9/2) and the negative-parity yrast band with configuration pi(P-3/2, f(5/2)) circle times nu(9/2) are compared with experimental data. The interpretation within the projected shell model shows that the signature inversion displayed in the positive-parity yrast band in this nucleus is a signal of a substantial quadrupole shape change with increasing spin where the nucleus evolves from a prolate shape at low spin through a triaxial shape to an oblate shape at high spin. In addition, we also specify the nuclear shape for these two bands

Uncertainties on gamma-ray energies and intensities measured in the decay of 83Sr

We analyze once again the γ singles spectra and γ-γ-t coincidence spectra following the β++EC decay of 83Sr. Multipeaks are carefully separated and many γ transition cascades are clearly obtained in the work. As a complement to our previous work, the uncertainties on γ-rays energies, γ-rays intensities and deduced level energies in the β++EC decay of 83Sr are given now.

High-Spin States and Level Structure in Stable Nucleus Strontium-84

High-spin states of 84Sr are populated through the reaction 70Zn (18O, 4n) 84Sr at the beam energy of 75 MeV. The measurements of excitation functions, γ-γ coincidences, directional correlations of oriented states (DCO) ratios and γ-transition intensities are performed using eight anticompton HPGe detectors and one planar HPGe detector. Based on the experimental results, we establish a new level scheme of 84Sr, in which 12 new states and nearly 30 new γ-transitions are identified in the present work. The positive-parity yrast band is extended to spin Iπ = 24+, while one negative-parity band is extended to spin Iπ = 19− and it is found that the even-spin and odd-spin members in high-spin states show the nature of signature staggering. The deformation of 84Sr is studied by calculating the total-Routhian-surfaces (TRS) of positive-parity yrast states in the cranked shell model formalism.

STABLE TRIAXIALITY IN GERMANIUM AND SELENIUM ISOTOPES

Total-Routhian-surface calculations by means of the pairing-deformation-frequency self-consistent cranked shell model have been carried out for germanium and selenium isotopes, in order to search f ...

New levels and transitions in (72)Ge observed in the (72)As(beta(+)+EC)(72)Ge decay

The decay of (72)As has been investigated by means of gamma-ray spectroscopy. The 72As nuclei were produced through the (72)Ge(p,n)(72)As reaction. The Compton-suppressed spectrometer and high-purity Ge detectors have been used in singles and in coincidence modes respectively to study gamma-rays in the beta(+) + EC decay of (72)As to (72)Ge. 79 gamma-rays, among which 3 were observed for the first time, were reported. A decay scheme of 72As including 1 new level is proposed that accommodates 77 of these transitions. Tentative spin and parity assignments are suggested for a number of levels according to the log ft values and gamma-branching ratios.

LOW-SPIN STATES OF 76Se EXCITED IN 76Br(β++EC)76Se DECAY

The decay of bromine-76 was studied using high resolution HpGe detectors in singles and coincidence mode. Bromine-76 was produced via two reactions: 75As(α,3n)76Br and 76Se(p,n)76Br. The results of these experiments verified the previously reported levels of 76Se. In addition to the previously described transitions and levels, 37 new γ-rays and 15 new energy levels were found for the first time.