Dipole bands in nucleus ^139Pm

High-spin states in nucleus ^139Pm have been studied using the reaction ^116Cd（^27Al, 4n）^139Pm. Two dipole cascades have been found. Spin and parity assignments were based on the Directional Correlation of Oriented Nuclei （DCO） ratios and systematic behavior in neighboring odd-proton nuclei. The level structures of ^139Pm are compared with those of the N = 78 isotone ^141Eu in which two dipole bands have been confirmed as magnetic rotational bands. The close similarity between them suggests that the dipole bands in ^139Pm may be magnetic rotational bands.     

125Cs的能级结构

通过116Cd(14N,5n),Ebeam=65MeV的核反应布居了125Cs的高自旋态.利用在束γ谱学实验方法,进行了γ-γ符合测量,使已知的125Cs核能级纲图得到了扩展,并且修正了某些组态的带头激发能.High-spin states in odd-A nucleus~(125)Cs have been studied via the~(116)Cd(~(14)N, 5n) reaction at 65 MeV bombarding energy. γ-γ coincidences were recorded with the NORDBALL detector array at Niels Bohr Institute in Denmark. After careful data analysis, most of the previously-known bands have been confirmed and 5 new rotational sequences have been identified. Spin/parity and configuration assignments are tentatively proposed for all of the observed bands. In addition, the bandheads of the 9/2~(+)and (1/2~...     

双奇核172Re的高自旋

对149Sm(27Al, 4n)172Re反应产生的172Re在束γ的实验数据进行了重新分析, 新发现了可归属于172Re的3个转动带, 由此建立了由6个转动带构成的172Re高自旋态能级纲图。依据相邻核的带结构知识和推转壳模型分析方法, 对新发现的3个转动带的准粒子组态进行了指定, 讨论了它们的转动特征。We have re analyzed the experimental data of in beam γ spectroscopy for 172Re via the 149Sm(27Al, 4n)172Re reaction. Three rotational bands have been newly found and assigned to 172Re. A new level scheme of 172Re, consisting of 6 bands, is thus presented. Based on the existing knowlegde from the neighboring nuclei and the cranked shell model, the quasiparticle configurtions have been assigned to the 3 newly observed bands and their structure properties have been dicussed.     

Observation of High-j Two-Quasiparticle Bands in Odd-Odd ^174Re

High spin states in ^174Re have been investigated via the ^152Sm （^27 Al, 5nγ） ^174Re reaction. Gamma-ray excitation functions, x-γ and γ-γ coincidences have been measured. Two rotational bands built on the πh9/2 × vi13/2 and πh11/2 × vi13/2 configurations have been identified and extended up to high-spin states. The relative spin and parity of the band levels have been unambiguously fixed due to observations of several inter-band transitions. Both the bands show the low-spin signature inversion, which is consistent with systematic expectations for the high-j two-quasiparticle bands in the A = 170 mass region.     

双奇核172Re高自旋态实验研究

利用149Sm(27Al,4nγ)172Re反应布居了形变双奇核172Re的高自旋态,用12套带有BGO反康普顿抑制的高纯锗探测器阵列进行了在束γ实验测量,首次建立了172Re由3个转动带构成的高自旋态能级纲图.研究和讨论了3个转动带的结构特征,基于已有的高自旋态核结构知识并通过系统学比较和分析指出它们的准粒子组态分别为πh11/2 νi13/2,πh9/2 νi13/2和 π1/2-[541] ν1/2-[521].发现前两个转动带在自旋小于18时其转动能级呈现反常的旋称劈裂.High-spin states in the odd-odd~(172)Re have been investigated via the~(149)Sm(~(27)Al, 4nγ)~(172)Re reaction through excitation functions, X-γ and γ-γ coincidence measurements. A level scheme consisting of three rotational bands have been identified for the first time extending the high-spin studies of A≈160 odd-odd nuclei to the currently lightest rhenium isotope. The three bands have been assigned to be built on the πh_(11/2) νi_(13/2), πh_(9/2) νi_(13/2 ) and π1/2~-\ν1/2~-\ configurations ...     

Chiral doublet bands in odd-odd nuclei

The criteria for chiral doublet bands based on one particle and one hole coupled to a triaxial rotor have been summarized. Candidate chiral doublet bands in A~100 and 130 odd-odd nuclei were checked against these chiral criteria. Two representative cases, nearly degenerate ΔI =1 doublet bands in ¹²⁶Cs and ¹⁰⁶Rh were investigated in the two quasiparticles coupled with a triaxial rotor model. After including the pairing correlation, good agreement has been obtained between the calculated results and the data available, which supports the interpretation of observed doublet bands as chiral bands.     

Structure of the πg7／2[404]7／2^＋ Band in Odd Proton Nucleus ^123I

High spin states of the odd proton nucleus ^123I have been populated in the reaction ^116Cd(^14N, 5n2p) at a beamenergy of 65 MeV. Two previously known positive-parity △I = 2 sequences have been extended up to 31/2^ and41/2^ . In addition, a number of △I = 1 transitions linking the two △I = 2 sequences have been observed. It issuggested that both the △I = 2 sequences are built upon the oblate πg7/2[404]7/2^ Nilsson configuration.     

Structure evolution along the yrast-line in 101pd

High-spin states in 101Pd have been investigated experimentally via the 76Ge(28Si,3nγ)101Pd reaction.The previously known bands based on the d5/2 and h11/2 neutron orbitals have been extended to higher-spin states,and two new structures have been observed.Spin and parity were assigned to the levels on the basis of the experimental results of the angular distribution of γ rays deexciting the oriented states.For the ground-state band,the E-GOS(E-Gamma Over Spin) curve strongly suggests a structure transition from vibration to rotation while increasing spin.     

Ultrahigh Spin Structures in 157,158,159Er

Rotational structures at ultrahigh spin in ^157,158,159 Er have been investigated with the configuration-dependent cranked Nilsson-Strutinsky approach. Configurations of observed bands are assigned and the corresponding deformations are given theoretically. The calculations suggest that one of ultrahigh spin bands in ^158 Er is triaxial highly deformed and the other is normal-deformed, while both ultrahigh spin bands in ^157Er are suggested to be triaxial highly deformed. The possible ultrahigh spin bands in ^159Er are predicted to be triaxial highly deformed and have shape coexistence in the same configuration. The configurations with two neutron holes in the Nose = 4 orbitals and two neutron holes in the h11/2 orbitals in ^159Er are favoured for ultrahigh spin states but unfavoured for band termination, which is similar to ultrahigh spin bands in ^157,15SEr.     

101Pd晕线的结构演化

High-spin states in ^101Pd have been investigated experimentally via the ^76Ge（^28Si, ^3nγ）^101pd reaction. The previously known bands based on the d5/2 and h11/2 neutron orbitals have been extended to higher-spin states, and two new structures have been observed. Spin and parity were assigned to the levels on the basis of the experimental results of the angular distribution of y rays deexciting the oriented states. For the ground-state band, the E-COS （E-Gamma Over Spin） curve strongly suggests a structure transition from vibration to rotation while increasing spin.     

Dipole bands in nucleus ~(139)Pm

High-spin states in nucleus 139Pm have been studied using the reaction 116Cd(27Al,4n)139Pm.Two dipole cascades have been found.Spin and parity assignments were based on the Directional Correlation of Oriented Nuclei(DCO) ratios and systematic behavior in neighboring odd-proton nuclei.The level structures of 139Pm are compared with those of the N =78 isotone 141Eu in which two dipole bands have been confirmed as magnetic rotational bands.The close similarity between them suggests that the dipole bands in 139...     

Dipole bands in nucleus ~(139)pm

High-spin states in nucleus (~139)Pm have been studied using the reaction ~(116)Cd(~(27)Al, 4n)~(139)Pm. Two dipole cascades have been found. Spin and parity assignments were based on the Directional Correlation of Oriented Nuclei (DCO) ratios and systematic behavior in neighboring odd-proton nuclei. The level structures of ~(139)pm are compared with those of the N = 78 isotone ~(141)Eu in which two dipole bands have been confirmed as magnetic rotational bands. The close similarity between them suggests that the dipole bands in ~(139)Pm may be magnetic rotational bands.     

High-Spin Level Scheme of Odd-odd 142Pm

The level structure of doubly odd nucleus ¹⁴²Pm has been studied via the ¹²⁸Te(¹⁹F,5nγ)¹⁴²Pm reaction in the energy region from 75 to 95MeV. In-beam γ rays were measureed including the excited function, γ-ray singles and γ-γ coincidences in experiment. The level scheme of ¹⁴²Pm has been extended up to excitation energy of 7030.0keV including 25 new γ rays and 13 new levels. Based on the measured γ-ray anisotropies, the level spins in ¹⁴²Pm have been suggested.     

Shape co-existence and structural evolution of the Vi13/2 band in 157Yb

The high-spin states of 157Yb have been studied via the reaction of 144Sm(16O, 3n) at 16O energy of 90 MeV using techniques of in-beam γ-ray spectroscopy. Measurement of γ-γ-t coincidences was performed with 11 BGO(AC)HPGe detectors. Based on the γ-γ coincidence relationships and the measured results of γ-ray anisotropies and DCO ratios, the level scheme for 157Yb was established. The shape co-existence and structural evolution of the Vi13/2 band with increasing angular momentum in 157Yb have been discussed. The systematics of the Vi13/2 bands in the N = 87 odd-A isotones have been compared.     

Shears bands in 112In

A new level scheme of 112In have been established up to 6.8 MeV in excitation energy and to a tentative spin of (21+) through the reaction 110Pd(7Li,5n)112In at a beam energy of 50 MeV. In-beam measurements involving γ-γ coincidences and directional correlation of oriented states were performed. M1 bands consisting of/△I = 1 dipole transitions have been observed. Possible quasiparticle configurations suggest that these bands are similar to the shears bands observed in Pb nuclei.     

High spin band structure in 139Nd

High-spin states in 139Nd nucleus have been reinvestigated with the reaction 128Te (16O, 5n) at a beam energy of 90 MeV. The level scheme has been expanded with spin up to 47/2 h. At the low spin states,the yrast collective structure built on the vh(-1)(11/2) multiplet shows a transitional shape with γ≈32° according to calculations of the triaxial rotor-plus-particle model. Three collective oblate bands with γ～-60° at the high spin states were identified for the first time. A band crossing is observed around hw ～0.4 MeV in one oblate band based on the 25/2- level.     

Rotational Bands in Odd-Odd 174Re

High spin states in ¹⁷⁴Re have been studied via the ¹⁵⁹Tb (²⁰Ne, 5nγ) ¹⁷⁴Re reaction through excitation function, X-γ and γ-γ coincidence measurements. A stretched E2 cascade has been identified and assigned to be the doubly decoupled band band on the л1/2^－[541]⊙v1/2^－[521] configuration. Other two bands with semidecoupled and strongly coupled characters have been found and their quasiparticle configurations are qualitatively discussed.     

Structure of high-spin states in 143Pm

High-spin states of ¹⁴³Pm have been studied in the reactions ¹⁴¹Pr(α, 2n)¹⁴³Pm and ¹⁴³Nd(d, 2n)¹⁴³Pm by means of in-beam spectroscopy. The level scheme, spin and parity assignments are based on results obtained from singles γ-ray spectra, conversion electron spectra, prompt and delayed γ-γ coincidences, γ-ray angular distribution and linear polarization measurements. Positive- and negative-parity states with energies up to 4580 keV and spins up to $\text{25}\text{2}$ have been established including 22 new levels. For two nanosecond isomeric states the nuclear spin precession in an external magnetic field was observed providing the following g-factors:

$\text{g(}\text{11?}\text{2}\text{, 959.7 keV)=1.14(9), g(}\text{15+}\text{2}\text{, 1898.3 keV)=1.00(7).}$

The experimental results are well understood by calculations which have been performed in the framework of the shell model (for positive-parity states of 11 valence protons above a Z = 50, N = 82 core) and of the cluster-vibration model (for 3 holes in a Z = 64, N = 82 core). In the case of positive-parity states no evidence for particle-core coupling could be found, while the negative-parity states could qualitatively be understood within the particle-core coupling picture.     

The decay of 4 min 158Tm

The decay of 4 min ¹⁵⁸Tm has been investigated with on-line mass-separated samples obtained from the Orsay ISOCELE separator. Measurements of γ-rays, conversion electron lines and γ-γ bi-dimensional coincidences were performed. About 180 transitions were ascribed to the decay and two thirds of them were placed in a decay scheme. The β-band and the γ-band were identified with bandheads situated at 806.40 and 820.13 keV respectively. In addition, a number of other vibrational bands (β-γ, β-β, K^π = 0^? and 1^?) are proposed. The decay properties of those bands are discussed in the framework of current nuclear models. The log ft values suggest a 2^? assignment for ¹⁵⁸Tm with the possible configuration (p404J↓-n521↑).