Study of Signature Inversion in the πi13/2 νi13/2Bands of Odd Odd Nuclei

High-spin states in odd-odd nuclei of ^176,178Ir and ¹⁸²Au have been studied experimentally using heavy-ion- induced fusion-evaporation reactions and standard in-beam γ-ray spectroscopic techniques. Rotational bands built on the πi_13/2 νi_13/2 configuration have been observed. In addition, on the basis of level spacing systematics, spin assignments have been proposed for the πi_13/2 νi_13/2 band in ¹⁸⁴ Au,which was reported without spin assignments in previous study. It is pointed out that the πi_13/2 νi_13/2 bands in ^176,178Ir and ^182,184Au present a low-spin signature inversion. In the theoretical framework of 2-quasiparticle plus rotor model with p- n residual interaction, the signature inversion phenomenon in the πi_13/2 νi_13/2 bands has been discussed qualitatively. Theoretical investigations have been performed for the πh_9/2 νi_13/2 and πi_13/2 νi_13/2 bands using the cranked shell model. It is found that the signature inversions in both configurations can be well reproduced using the pairing and deformation self-consistent cranked Wood-Saxon calculations.     

Experimental Study of High-Spin States in Deformed Odd-Odd 180 Ir

High spin states in deformed odd-odd ¹⁸⁰Ir have been investigated using the ¹⁵⁴Sm (³¹P, 5nγ)¹⁸⁰Ir reaction through the measurements of excitation functions at 150, 155, 160, 165 and 170 MeV beam energies, K X-γ and γ-γ coincidences at 160 MeV. A new level scheme composed of 5 rotational bands has been established. According to the band structure characteristics and the deduced in band B(M1)/B(E2) ratios, the quasiparticle configurations and spin and parity have been proposed to the observed bands. The neutron AB crossing is observed at hω_c≈0.26 MeV for the π1/2^－[541]⊙ν1/2^－[521] and π1/2^－[541]⊙ν5/2^－[512] bands. This AB crossing frequency is close to that in the ν5/2^－[512] band of ¹⁷⁹Os indicating the loss of intruder nature of the π1/2 - orbit. Gradual alignment gain in both the π9/2^－[514]⊙ν7/2⁺[633] and π9/2^－ν5/2^－[512] bands is observed which is similar to the low spin anomaly in alignment in the πh_11/2,πd_5/2 and πi_13/2 bands of neighboring Ir and Re isotopes. Different alignment properties have been discussed in the framework of cranked shell model, and a larger quadrupole deformation is suggested for the bands with π9/2^－[514] orbit involved.     

Study of 1/2[660](πi13/2) Rotation Band in 179Au

High-spin states in ¹⁷⁹Au have been studied experimentally using the ¹⁴⁹Sm(³⁵Cl,5n) heavy-ion fusion-evaporation reaction at beam energies of 164—180MeV. Measurements of γ-ray excitation functions, X-γ coincidences and γ-γ-t coincidences were performed with 13 BGO(AC)HPGe and 3 LOAX detectors. Based on these measurements, a rotational band built on the 1/2[660](πi_13/2) Nilsson state has been established for the first time, and this band has been assigned to ¹⁷⁹Au according to the systematic of level structure in odd-A Au nuclei. Properties of the 1/2[660](πi_13/2) band in odd-A Au nuclei are discussed with an emphasis on the band-head energy while changing the neutron number.     

A New Level Scheme of 127I

Study of in beam γ ray spectroscopy of ¹²⁷I has been performed using ¹²⁴Sn(⁷Li, 4n)¹²⁷I reaction at 32 MeV beam energy. A new level scheme of ¹²⁷I has been established including 25 new levels and 52 new γ transitions. Negative parity levels based on 11/2^－ π h_11/2 particle state have been observed up to (35/2^－) extending our knowledge of decoupled structures to the heavier iodine isotope. Two ΔI=2 yrast positive-parity levels have been proposed to be associated mainly with the πg_7/2 configuration due to observations of several strong inter band transitions. Two weakly populated ΔI=2 positive parity levels and a high-lying ΔI=1 cascade have been newly identified and tentatively assigned as πd_5/2 one-quasiparticle and three quasiparticle bands, respectively.     

Experimental Evidence for the Superdeformation in 81Rb

High-spin states in ⁸¹Rb were populated in the ⁵⁵Mn(³⁰Si, 2p2n) reaction at 130 MeV. Prompt γγγ-charged particle coincidences were observed using the GASP spectrometer in conjunction with the ΔE-E silicon ball (ISIS). A superdeformed band consisting of seven γ-ray transitions has been identified. The dynamic moment of inertia for the band is constant with a value of approximately 26.7 h²/MeV throughout the whole observed rotational frequency. This band is interpreted to have a π5¹v5² intrinsic intruder configuration with a quadruple deformation β₂ of 0.51.     

Configuration-Dependent Bands in 169Re

High-spin states in ¹⁶⁹Re were studied and resulted in the identification of a strongly coupled band based on the 9/2^－[514] Nilsson state and a decoupled band built on the h_9/2 intruder proton orbital (nominally 1/2^－[541]). The cranked shell nodel calculations present configuration-dependent deformations that can explain the different band crossing frecpiencies. The experimental 9/2^－[514] band in Re shows the largest signature splitting at low spin among the known odd mass Re isotopes. After the alignment of a pair of the i_13/2 neutrons, the phase of the splitting is inverted with a significantly reduced amplitude. Additionally, a three-quasipariticle band was observed and assigned to be built likely on the π9/2^－[514]⊙AE configuration.     

Collective Band Structures in Neutron-Rich Odd-A 145,147Ce Nuclei

Through study of the prompt r-rays emitted in the spontaneous fission of ²⁵²Cf, high spin states of neutron-rich odd-A ^145,147Ce nuclei have been investigated. The levels in ¹⁴⁷Ce have been extended. A collective band in ¹⁴⁵Ce have been identified for the first time. The results from the particle rotor model calculations indicate that the yrast bands in ¹⁴⁵Ce and ¹⁴⁷Ce originate from vi_13/2 orbital coupling and the ground states of ¹⁴⁵Ce and ¹⁴⁷Ce originate from (vh_9/2,vf_7/2) and vh_9/2 configiration, respectively. No obvious octupole deformation was observed in these two isotopes, but a side band obtained in ¹⁴⁷Ce may show some octupole correlations.     

三硝基甲苯起爆机理实验研究

 用单脉冲化学激波管实验方法,使用自由基清扫剂和对比速率,测定了邻位和对位硝基甲苯在高温下,裂解瞬间（500 μs） 的化学反应机理,并测定了化学反应速率常数。作为邻位硝基甲苯的同分异构体,对位硝基甲苯的主要裂解通道与其不同。通过实验发现了邻位硝基甲苯的裂解重要通道,测到它的产1氧-2氮-3,4-环丁二稀基异嚙唑（Anthranil） 在瞬间随温度变化生成和很快消失的过程。由此,测得这一化学性质极不稳定的产物的消失速率常数为：k(Anthranil)＝3.7×10¹⁵·exp(－25 800/T) s^-1。分析这一过程的机理,认为第一步是硝基甲苯的裂解,第二步是Anthranil的生成,第三步是Anthranil中的N－O键的断裂。     

Collective Bands in Neutron-Rich 107Ru Nucleus

Through measuring prompt γ-rays emitted in the spontaneous fission of ²⁵²Cf with higher statistic data,level structures in the neutron rich,odd A¹⁰⁷Ru nucleus have been re investigated. New level scheme of ¹⁰⁷Ru has been established. The ground state band was extended with spin up to 27 2h. The νh_11/2 band structure observed in our previous publication has been confirmed and extended. These results clear up the inconsistence between our earlier work and results from another experiment published recently. A collective band built on (9/2^－) level has been observed for the first time. Some important features of the level scheme have been discussed.     

Measurement of 125Ba High Spin States

The high spin states of ¹²⁵Ba populated via the ¹⁰⁹Ag(¹⁹F,3n) reaction are measured by using a BGO Compton suppressed HPGe detector array.The negative and positive parity bands built respectively on the h_11/2 and g_7/2 neutron hole states are extended to 35/2^－ and 23/2⁺.Backbending occurs in both signature branches of the negative band at the frequencies close to that of the ¹²⁴Ba yrast band.An onset of backbending in the positive band has been seen.     

Complex Fragments Emitted in Reactions of 46．7MeV/u 12C on 197Au,115In and 58Ni

Energy spectra of complex fragments emitted in the reactions of 46.7MeV/u ¹²C with different targets ¹⁹⁷Au,¹¹⁵In and ⁵⁸Ni have been measured by telescopes,consisting of a gis ionization counter followed by a position Sensitive semiconductor detector.Tha most probable kinematical energies.E_p of complex fragments and temperature parameters of long－live intermediate systems have been deduced by complex fragment ernergy spectra.The experimental values of E_p are lower than the calculated ones by E=V_coul+2T.The experimental values of complex fragment yields can be reproduced by simple A.Friedman statistical evaporation model satisfactorily.     

ANALYSIS OF QUASI-△33 DOORWAY STATE MODEL IN π NUCLEUS SCATTERING

Under Quasi-△₃₃ Doorway state model of π nucleus scattering, the differential cross sections and total cross sections of elastic π-⁴He and π-⁴⁰Ca at the different incident energies, (T_x^lab=110, 150, 180, 220, 260 MeV for π-⁴He, T_x^lab=115.5, 163.3, 241.0 MeV for π-⁴⁰Ca) are calculated. The approximate agreement between the theoretical results and experimential data is arrived at.We evaluate further the correction of spin-orbite coupling effects for π-⁴He, and the better agreements with experimential data are obtained.     

几种材料的等效粘性系数、初始可动位错密度和拖曳应力

 基于LY12铝、MB₂镁、铅、2^#铁和不锈钢等几种材料的弹性前驱波幅度随传播距离衰减的实验结果,应用含位错参量的速率相关本构方程,按照Gilman提议的位错运动速度的热激活模型,得出了LY12铝、MB₂镁、铅的可动位错密度N₀和拖曳应力τ₀的下限值分别为10⁶ cm^-2和0.1 GPa量级,不锈钢的N₀和τ₀为10⁸ cm^-2和1.5 GPa量级。根据弹性前驱波幅度衰减曲线,还得出了2^#铁、不锈钢的有效粘性系数μ的上限值为10⁴ Pa·s量级。LY12铝、MB₂ 镁的有效粘性系数μ的上限值为10³ Pa·s量级。     

Identification of Collective Bands in Neutron-Rich 113Ru Nucleus

Through measuring high-fold prompt γ- ray coincidence events following the spontaneous fission of 252 Cf with the Gammasphere detector array, new level scheme in the very neutron-rich odd-A 113Ru nucleus has been established. An intruder collective band based on 11/2^－ level has been identified with spin up to 31/2 k and excitation energy 3.6 MeV. This band most probably originates from vh_11/2. intruder orbital. Another collective band probably built on 9/2^－ level is also observed. Some important characteristics of the collective bands have been systematically discussed.     

DISCOVERY OF MULTIPLE,COLLECTIVE BAND STRUCTURES IN NUCLEI WITH A=60—80

Recent studies of levels in even-even ^68,70,72Ge,^70,72,74Se,^74,76,78,80Kr and ⁶⁵Ga and ⁷⁴Br have led to the discovery of a wide variety of different collective band structures.These include bands built on near spherical ground states and excited more well de-formed shapes that may include triaxial shapes,rotation-aligned bands built on thesame orbital （g_（9/2））² for both protons and neutrons,RAL negative parity bands witheven and odd spins,and ΔI=1 γ-type vibrational bands in even-even nuclei.As recent as 1974,a survey of the energy level in the even-even Ge and Se iso-topes^[1] revealed little was known above a spin of 4⁺ （see for examples Figs.1 and 2 of Ref.1）.With the exception of the unusally low-lying excited 0⁺ states in ^70,72Ge,first discovered in ⁷²Ge in 1948 at Vanderbilt^[2],the theoretical treatment of thesenuclei was limited primarily to some variation of the vibrational model.However,very recently there has been a surge of information on nuclei in this region that hasrevealed fascinating new features and also provided new insight into the excited 0^+’states.Particularly striking are the multiple,independent and highly collective bandstructures which we have discovered in our in-beam γ-ray spectroscopy studies fol-lowing heavy-ion induced reaction.Evidence for and the theoretical understandingof the richness of the collective band structures that are found in our studies of^68,70,72Ge （Refs.3—6）,^70,72,74Se （Refs.7—13） and ^74,76,78,80Kr （Refs.14—18）,as illustratedby the at least seven different bands found in our studies of the levels of ⁶⁸Ge ⁷⁴Se,and ⁷⁶Kr （Figs.1—3）,are described in this paper.These multiple structures includethe following:a) coexistence of ground bands built on near-spherical shapes andexcited bands with larger deformation built on O^+′ band heads;b) bands with 8⁺ band heads interpreted as rotation-aligned,RAL,bands built on both neutron and/orproton （g_（9/2））² quasiparticle configurations coexisting with the ground-state band;c)RAL neutron and proton odd-parity bands formed from coupling of a g_{（9/2 ）}quasipar-ticle and a p_（1/2）,p_（3/2） or f_（5/2）,quasiparticle with the core;d) ΔI=1 even-parity bands,which are best characterized as gamma-vibrational bands;and e) additional bandswhose nature are presently not known.     

Correspondence between phenomenological and IBM-1 models of even isotopes of Yb

Energy levels and the reduced probability of E2–transitions for ytterbium isotopes with proton number Z=70 and neutron numbers between 100 and 106 have been calculated through phenomenological(Ph M)and interacting boson(IBM-1)models.The predicted low-lying levels(energies,spins and parities)and the reduced probability for E2–transitions results are reasonably consistent with the available experimental data.The predicted low-lying levels(gr–,β1–andγ1–band)produced in the Ph M are in good agreement with the experimental data compared with those by IBM-1 for all nuclei of interest.In addition,the phenomenological model was successful in predicting theβ2–,β3–,β4–,γ+2–and 1+–band while it was a failure with IBM-1.Also,the 3–band is predicted by the IBM-1 model for172Yb and174Yb nuclei.All calculations are compared with the available experimental data.     

New band structures in 107Ag

High spin states in ¹⁰⁷Ag are studied via the ¹⁰⁰Mo(¹¹B, 4n)¹⁰⁷Ag reaction at an incident beam energy of 60 MeV. Prompt γ-γ coincidence and DCO ratios are measured by the detector arrays in CIAE. The level scheme has been updated and a new negative band belonging to ¹⁰⁷Ag is identified. The new negative side band has been constructed and its configuration is tentatively assigned to πg_9/2 νh_11/2(g_7/2/d_5/2).     

Gamow-Teller Transitions of Nuclei With A=147-153

In this paper the Gamow-Teller transitions are systematically investigated for nuclei with A=147-1.53 in terms of the shell-model. These nuclei have only GT decay channel π1h_11/2→v1h_9/2. The overall comparisons of the experimental reduced probabilities B_exp(GT) with the calculated B_cal(GT) show that there is a quenching factor γ² with optimum value 0.17±0.05 in this mass region.     

Measurements of g-Factor of Rotational Band States in 82Sr

The g-factors of the positive parity rotational states up to spin I = 8^＋ for the ground state band in even-even nuclei S2Sr have been measured by a transient-magnetic-field ion implantation perturbed angular distribution method. The experimentally measured 9-factors increase with the increasing spin along the band and show that the g9/2 proton aligns only and the alignment starts from I =6^＋. The measured g-factors also indicate that the nuclei ^82Sr gain their spins by the quasi-proton alignment at higher spin.     

Na填充型方钴矿化合物CoSb3的高压合成及电输运特性研究

 利用高压合成方法,在压力为2 GPa、温度为900 K的条件下,以NaN₃作为添加剂,成功地合成出了Na填充型的方钴矿化合物CoSb₃。X射线衍射（XRD）研究结果表明,当Na填充量达80%时,合成的Na填充型方钴矿化合物CoSb₃仍为单相方钴矿结构,没有Na和NaN₃等杂质峰。在室温下对不同Na填充量的样品进行了电阻率（ρ）和Seebeck系数（α）的测试,研究了不同Na填充量对样品电阻率、Seebeck系数和功率因子（α²σ）的影响。研究结果表明：室温下,样品的电导率随Na填充量的增加而增大,Seebeck系数的绝对值随Na填充量的增加而减小。当Na填充量为0.4时,样品获得了最高的功率因子（8.72 μW·cm^-1·K^-2）,此值高于He等报道的利用热压法制备的CoSb₃的值。填充量对样品电输运特性的影响规律与Pei等研究的K填充型CoSb₃的研究结果相一致。上述研究结果表明,高压合成技术有利于提高填充型方钴矿化合物的填充量,并有效地提高样品的电输运特性。