Criteria of the Spin Assignment of Rotational Band

Based on the very general properties of the rotational band of axially symmetric nucleus, some rules of the I variation of the kinematic and dynamic moments of inertia are obtained, which may serve as the effective criteria of the spin assignment of rotational band. Extensive analysis of large amount of ro tational bands (below bandcrossing) of normally deformed eveneven nuclei whose spins were established shows that these rules do hold without exception. The spins of the yrast superdeformed bands of even-even nuclei in the actinide region (fission isomeric bands), and in the A～190, 150 regions are analyzed also. The spin of the lowest observed level of the yrast superdeformed band in ¹⁵²Dy is determined to be I₀ = 26, rather than I₀ = 22 or 24.     

q变形转动惯量对148Gd核超形变带的描述

利用q变形转动惯量的转子模型,系统地计算了¹⁴⁸Gd核6个超形变带的E2r跃迁能谱以及相应的动力学转动惯量随转动频率的变化关系.计算结果表明,q变形转动惯量的转子模型不仅能较精确地描述超形变晕带,而且可以描述超形变激发带.     

丰中子锶同位素的投影壳模型研究

利用考虑跨壳激发的投影壳模型（PSM）方法,研究了质子数Z=38、中子数N=63和64大形变丰中子101,102Sr同位素的结构性质。主要计算了转动谱、转动惯量和电磁跃迁性质等（如B（E2）和g因子）,并与相应的实验数据进行系统比较和相关的理论预言。结果表明,PSM可以利用理论计算的能带图解释101,102Sr同位素的转动惯量、电磁跃迁随自旋的变化,分析晕带的结构。PSM理论可以很好地再现实验结果,说明PSM方法及其采用的有效相互作用可以外推研究丰中子核区101,102Sr同位素的原子核结构。对于101,102Sr同位素,核子开始填布质子g_9/2和中子h_11/2轨道,通过更为仔细地分析能带图中来自质子g_9/2和中子h_11/2轨道对各转动带的组态成分的贡献,清晰地表明丰中子核结构性质对不同核子填布的依赖。Recently, we have carried out systematically studies on the structural properties of proton number Z=38, neutron number N=63 and 64 neutron-rich isotopes 101,102Sr by using the projected shell model (PSM) with consideration of cross shell excitation. The rotation spectra, the moment of inertia and the electromagnetic transition properties (such as B(E2) and g-factor) are calculated and compared with the corresponding experimental data in this paper. Furthermore, more high spin states are predicted in the calculation and expected to be confirmed experimentally. The results show that the PSM can not only well analyze the structural properties of yrast bands in 101,102Sr but also interpret the variation of the moment of inertia, electromagnetic transition with spins in terms with the theoretical band diagram. The good agreement with the experimental data suggests that the PSM with the adopted effective interactions can be generalized to study the nuclear structure of 101,102Sr isotopes in neutron-rich mass region. For 101,102Sr isotopes, the nucleons begin to fill proton g_9/2 and neutron h_11/2 orbital, the dependence of nuclear structure and properties on the different orbital occupies is described by carefully analyzing the contribution from proton g_9/2 and neutron h_11/2 orbital to the configuration of rotational bands in band diagram.     

Underlying Physics of Identical Odd-and Even-Mass Bands in Normally Deformed Rare-Earth Nuclei

The microscopic mechanism of the identical odd-and even-mass number nuclear bands in normally deformed rare-earth nuclei was investigated using the particle-number conserving (PNC) method for treating nuclear pairing correlation. It was found that the odd particle of an odd-A identical band always occupied a cranked low j and high Ω Nilsson orbital (e.g. proton [404]7/2, [402]5/2). On the contrary, if the odd particle occupies an intruder high j orbital (e.g. neutron [633]7/2, proton [514]9/2), the moment of inertia of the odd-A band was much larger than that of neighboring even-even ground state band. The observed variation of moment of inertia (below bandcrossing) was reproduced quite well by the PNC calculation, in which no free parameter was involved. The strengths of monopole and Y₂₀ quadrupole interactions were determined by the experimental odd even differences in binding energy and bandhead moment of inertia.     

Band head spin assignment of Tl isotopes of superdeformed rotational bands

The Variable Moment of Inertia (VMI) model is proposed for the assignment of band head spin of super deformed (SD) rotational bands, which in turn is helpful in the spin prediction of SD bands. The moment of inertia and stiffness parameter (C), were calculated by fitting the proposed transition energies. The calculated transition energies are highly dependent on the prescribed spins. The calculated and observed transition energies agree well when an accurate band head spin (I ₀) is assigned. The results are in good agreement with other theoretical results reported in literature. In this paper, we have reported the band head spin value 16 rotational band of super deformed Tl isotopes.     

Evidence for an i13/2 neutron band in133Sm

A rotational band of nine γ-rays has been observed in¹³³Sm. The moment of inertia of the band indicates that it has a higher deformation than expected for states in nuclei in this region. The properties are such that it can be interpreted as being due to the odd neutron occupying the ν i2/13 nn intruder orbital. This is the first evidence for the occupation of this orbital in nuclei with neutron number N<73.     

双奇核~(170)Re高自旋转动带分析(英文)

通过重离子熔合蒸发反应142Nd(32S,1p3nγ)170Re布居了缺中子双奇核170Re的高自旋激发态,识别出了该核的一条转动带并建议了其组态为πh1/2 νi13/2。基于对同中子素能级系统性、旋称反转系统性、带内B(M1)/B(E2)、准粒子Routhians、动力学转动惯量和Total Routhian Surface(TRS)等带结构特征的详细分析和讨论,进一步确认了对A=170核区目前最缺中子双奇核高自旋转动带组态、宇称和自旋值的指定。     

Contrasting high-spin yrast bands in 172Os and 174Os and an unexpected low-frequency anomaly in 172Os

The yrast bands of the neutron deficient isotopes ¹⁷²Os and ¹⁷⁴Os have been identified to spins of about 24. The yrast band in ¹⁷⁴Os shows no bandcrossing anomalies, confirming the shell effect observed in other N = 98 nuclei. In contrast, a strong backbend observed at a frequency of about 0.26 MeV in ¹⁷²Os is attributed to the s-band crossing. A weaker band-crossing is also observed at a lower frequency, about 0.24 MeV, in ¹⁷²Os. This unexpected anomaly may be due to either a deformation effect, or to a change in the s-band structure.     

The rotational quasi-continuum in specific configurations: high-K states and superdeformation

The analysis of the fluctuations of the counts of unresolved γ-γ energy spectra can extend our knowledge of the rotational motion at high angular momentum and excitation energy above the yrast band. Detailed studies of the rotational quasi-continuum built on specific intrinsic nuclear configurations are here discussed. First, the validity of the K-selection rules in the quasi-continuum region is investigated in the case of the normal deformed nucleus ¹⁶³Er. The γ cascades feeding into low-K and high-K bands are analyzed studying variance and covariance of the spectrum fluctuations. Low-K bands are found to be fed by a much larger effective number of cascades than high-K bands, while the covariance between pairs of gated spectra shows that the cascades feeding into low-K bands are different from those feeding into high-K bands. These findings suggest a persistence of K-selection rules in the region of excitation energy and angular momentum probed by the rotational decay of ¹⁶³Er. As a second case, the existence of a rotational quasi-continuum in the super deformed well of ¹⁴³Eu is discussed. An intense bump of rotationally correlated transitions is observed to develop as function of fold in the high spin region of gated spectra. Fold distribution, angular anisotropies, moment of inertia and life time show that the bump consists of fully damped super deformed transitions. This gives experimental evidence of damped rotational motion up to several MeV excitation energy above the super deformed yrast line.     

Hf高自族态推转壳模型PNC方法研究

用推转壳模型ＰＮＣ方法研究了１６６Ｈｆ９４－１７０Ｈｆ９８核，计算了这三个核晕带和次晕带间的带交叉频率、带间互作用强度、顺排角动量和转动惯量等，并与实验值作了比较，结果表明在Ｎｉｌｓｓｏｎ势参数完全按照Ｌｕｎｄ系统学选取的情况下，理论计算值与实验值符合得较好．     

M1 Character of unresolved continuum transitions from X-ray multiplicity measurements

We have measured the X-ray multiplicities of the transitions deexciting the quasi-continuum region as a function of the input spin for deformed and transitional erbium isotopes obtained in (⁴⁰Ar,xn) reactions. Combined withγ-ray angular distribution studies, these measurements clearly show the occurrence of a magnetic dipole component in the energy region 300–800keV. The spin dependence of this “bump” is quite different in deformed and transitional nuclei. In the latter case, a sudden increase in the quasi-continuumK electron multiplicity arises for spins higher than 35? and is strongly correlated to the occurrence of collective modes in these nuclei at the same spins. It is suggested to correspond to collective behavior of bands built on yrast states of single particle nature.     

Prompt alpha decay of a well-deformed band in (58)Ni

Two excited well-deformed bands have been observed in the semi-magic nucleus (58)Ni. One of the bands was observed to partially decay by emission of a prompt discrete alpha particle that feeds the 2949 keV 6(+) spherical yrast state in the daughter nucleus (54)Fe. This constitutes the first observation of prompt alpha emission from states lying in the deformed secondary minimum of the nuclear potential. gamma-ray linking transitions via several parallel paths establish the spin, parity, and excitation energy of this deformed band in (58)Ni.     

Spectroscopy of 166W and 167W and alignment effects in very neutron-deficient tungsten nuclei

High-spin states in ¹⁶⁶W and ¹⁶⁷W were populated by the reactions ¹⁴²Nd(²⁸Si,4n)¹⁶⁶W, ¹⁴²Nd(²⁸Si,3n)¹⁶⁷W and ¹⁴⁷Sm(²⁴Mg,4n)¹⁶⁷W. From the γ-decay the yrast band and a side band (with assumed negative parity) were identified to high spins. There is evidence for a second side band in ¹⁶⁷W. The observed backbend of the yrast sequences and band-crossing anomalies in the side bands are discussed in conjunction with cranked-shell-model calculations. A systematic comparison is made between the yrast bands of ^166,167,168W in order to understand the structure of the second backbend in ¹⁶⁸W.     

稀土变形奇A核173,175Hf的多准粒子高K转动带的粒子数守恒分析

用处理推转壳模型的粒子数守恒方法分析了稀土奇A变形核^173,175Hf的3准粒子和5准粒子高K转动带,包括转动惯量、顺排角动量,以及推转Nilsson能级上的粒子填布几率随转动角频率的变化.计算中无自由参数.实验观测结果在计算中得到较好地重现.分析了多准粒子带与相邻偶偶核基态带的转动惯量变化规律不同的微观机制.在这里Fermi面邻近高j闯入态的堵塞效应起了举足轻重的作用.     

Particle-Number Conserving Analysis for High K Multi-Quasiparticle Bands in Odd-A Deformed Nuclei 173,175Hf

Using the Particle-number Conserving (PNC) method for treating the cranked shell model, the high K multi-quasiparticle bands in odd-A deformed nuclei ^173,175Hf are analyzed, including the variation with rotational frequency of the moment of inertia, angular momentum alignment and occupation probability of each cranked Nilsson orbital. No free parameters are involved in the PNC calculation and the experimental results are reproduced well. The microscopic mechanism of the difference between the multi-quasiparticle high K bands and the yrast bands in neighboring even-even nuclei is investigated, where the blocking effects of high j intruder orbitals near the Fermi surface play a crucial role.     

Rb晕带signature反转的机理

将角动量投影壳模型应用到84Rb核，对组态为πg9/2νg9/2的正宇称晕带和组态为π(p3/2,f5/2)νg9/2的负宇称晕带理论计算和实验结果进行了比较，特别是对正宇称晕带中的signature反转机理进行了探讨.角动量投影壳模型计算显示正宇称晕带中的signature反转是原子核随自旋增加形状发生变化的信号，其间原子核从低自旋的长椭球通过三轴形变变到高自旋的扁椭球.此外，还确定了此两带的原子核形状.     

High-spin yrast and non-yrast bands in 176Os, 178Os and 180Os

High-spin yrast and non-yrast states have been identified in ¹⁷⁶Os, ¹⁷⁸Os and ¹⁸⁰Os using (¹⁶O, xn) reactions, and γ-ray techniques. Band crossing anomalies are observed in each of the positive-parity yrast bands. The magnitude of these anomalies decreases with decreasing neutron number, an effect attributed to the change in the moment of inertia of the ground state rotational bands. A 23 ns isomer, predominantly K^π = 7^?, is identified at 1930 keV in ¹⁸⁰Os. The configuration of this isomer is discussed on the basis of the properties of its rotational band. Negative parity, odd and even spin, sideband sequences are observed in each isotope. Their relationship to rotation-aligned octupole and 2-quasiparticle bands is discussed from their excitation energies, band spacings, and decay properties. Detailed calculations for Coriolis mixed bands are carried out for the likely 2-quasiproton and 2-quasineutron configurations. An anomaly observed at spin 17 in the odd-spin negative-parity sequence in ¹⁸⁰Os is attributed to a band crossing with a fourquasiparticle configuration.     

Band head spin assignment of superdeformed bands in 86Zr

Two parameter expressions for rotational spectra viz. variable moment of inertia (VMI), ab formula and three parameter Harris ω² expansion are used to assign the band head spins (I₀) of four rotational superdeformed bands in ⁸⁶Zr. The least-squares fitting method is employed to obtain the band head spins of these four bands in the A~80 mass region. Model parameters are extracted by fitting of intraband γ-ray energies, so as to obtain a minimum root-mean-square (rms) deviation between the calculated and the observed transition energies. The calculated transition energies are found to depend sensitively on the assigned spins. Whenever an accurate band head spin is assigned, the calculated transition energies are in agreement with the experimental transition energies. The dynamic moment of inertia is also extracted and its variation with rotational frequency is investigated. Since a better agreement of band head spin with experimental results is found using the VMI model, it is a more powerful tool than the ab formula and Harris ω² expansion.     

127La转动带及带终止

组态相关推转壳模型 Nilsson势研究了 C.M.Parry组最近用 EUROBALL谱仪观测到的 12 7La高自旋态结构 .实验上观测的 12 7La的宇称和辛量子数为 (π,α) =(+,- 1 /2 )的带自旋达到(83/2 ) h.理论计算结果表明该带可能具有组态 π(h11/2 ) 2 ν(h11/2 ) 6.并且几乎达到该带的带终止理论预言值 I=47.5h.该带的形变在 I≤ 40 h内处于正常形变区 (ε2 ≈ 0 .2 2 ,γ≈ 0°) ,随着角动量的增加 γ值逐渐增加 ,直到 γ=60°时带终止. HJ4/9]The configuration dependent shell correction approach with cranked Nilsson potential is employed for explaining the experimental high spin spectra in 127 La. The experimental high spin band with parity and signature (+, -1/2) consists of two parts with a crossing around I =20 . It is most like to have the configuration [02, 6], π (h 11/2 ) 2 ν (h 11/2 ) 6 and almost reaching the maximum angular momentum at I =47.5 . It is in normal deformation region with ...     

Shape Coexistence and Band Termination in Doubly Magic Nucleus 40Ca

Shape coexistence and band structure near yrast line of the Z=N doubly magic nucleus ⁴⁰Ca have been investigated by the configuration-dependent cranked Nilsson-Strutinsky approach. The observed normal deformed and superdeformed bands are explained and the terminating states are confirmed by the calculations. The transition quadrupole moment Q_t of the calculated superdeformed band is in good agreement with the observed one at high spin. There is shape coexistence within the same configuration. Possible normal deformed and superdeformed bands with rotation around the intermediate axis in several interesting configurations of ⁴⁰Ca are discussed. Possible favored superdeformed band terminations in ³⁸Ca and ³⁸Ar are predicted. The experimental results in ³⁸Ar are discussed simply.