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1.
Band structures of 76Se and 78Se have been studied with the 74,76Ge(, 2nγ) 76,78Se reactions by using a variety of in-beam γ-techniques : γ-ray singles spectra, γ-ray excitation functions, γ-γ- t coincidences, γ-ray angular distributions and γ-ray linear polarizations. Spins and parities have been assigned uniquely for many new levels in 76Se and 78Se and four bands have been identified in both nuclei: (i) the ground-state band, (ii) a positive-parity ΔJ = 1 band built on the second 2+ state (γ-vibrational band), (iii) a negative-parity Δ J = 2 band built on the 3− state (octupole band) and (iv) a ΔJ = 2 band built on the high-lying J = 4 state. In addition, the second 8 + and 10+ states, which are possibly the lowest members of a band, have been found in both nuclei. Systematics of the band structures obtained are discussed. Level energies of the band members and B(E2) ratios for some of the inter-band transitions between γ- and ground-state bands have been calculated with the proton-neutron interacting boson model IBM-2 and a reasonable agreement with the present data has been obtained. 相似文献
2.
The level structure of 102Pd has been investigated using data collected with the Eurogam 2 array. Several cascades of γ-rays have been established up to high spins. Termination of rotational bands has been observed at Iπ = 28 − and 32 +, and tentatively at Iπ = 38 + and 42 +. The nucleus 102Pd is the first case where rotational bands built on valence space configurations are followed from spin close to zero up to termination and, at higher spins, a smooth rotational band which appears to terminate is built on core excited configurations. 相似文献
3.
Lifetimes of excited 0 + states in 166Er have been measured with the (n,n′γ) reaction. The first and second excited 0 + states have no significant collective enhancements of their decays, and their properties are suggestive of pair-type excitations rather than those of a β vibration or phonon excitation built on the γ vibration. The third excited 0 + state at 1934 keV has an enhanced decay to the ground state band with B( E2; 0 4+ → 2 gsb+) = 8.8 ± 0.9 W.u., consistent with that expected for a β vibration. 相似文献
4.
The static quadrupole moments of the first excited Jπ = 2 + states in 20Ne and 22Ne and the reduced electric quadrupole transition probabilities of these states to the ground states were measured via projectile Coulomb excitation. The quadrupole moments were deduced from the shapes of γ-ray angular distributions. The results are: Q( 20Ne, 2 +) = −0.20±0.05 b and Q( 22Ne, 2 +) = −0.11±0.05 b. The transition strengths were deduced from yield measurements and by comparison with the yields of target γ-rays. The results are: B(E2; 0 + → 2 +, 20Ne) = 0.037±0.003 e2 · b 2 and B(E2; 0 + → 2 +, 22Ne) = 0.025±0.002 e2· b 2. The results for the transition strengths are consistent with the results of accurate timing methods and resolve discrepancies between previous experiments. The results for the quadrupole moments are consistent with earlier measurements, although the mean values we obtain are slightly lower. The experimental measurements are compared with theoretical predictions and a detailed discussion is given of corrections to this type of reorientation experiment. 相似文献
5.
An 879.9(2) keV γ-ray transition has been identified following the β decay of 58V and assigned as the 2 +1→0 +1 transition in 58Cr 34. A peak in the energies of the first excited 2 + states for the even–even chromium isotopes is now evident at 56Cr 32, providing empirical evidence for a significant subshell gap at N=32. The appearance of this neutron subshell closure for neutron-rich nuclides may be attributed to the diminished π1 f7/2–ν1 f5/2 monopole proton–neutron interaction as protons are removed from the 1 f7/2 single-particle orbital. 相似文献
6.
Discussion Compton scattering on the new states we establish the following: The spin JP = 2 + state, an orbital excitation of ψ, must exist, and its coupling to the ψ(3084) is related to the coupling ψX(2800). A spin higher than 2 (probably 3) with negative charge conjugation must exist, and its couplings can be related to the ψ2 +γ and ψ′2 +γ couplings. This state might have a substantial radiative width to the 2 +. These results depend on a saturation assumption of the sum rules, which has always worked well. Its failure will also be of interest. 相似文献
7.
K-band electron spin resonance (ESR) at 4.3 K has revealed the dipole-dipole (DD) interaction effects between [1 1 1]P b centers ( *Si ≡ Si 3 defects with unpaired sp 3 hybrid [1 1 1]) at the 2 dimensional (1 1 1)Si/SiO 2 interface. This has been enabled by the perfectly reversible H 2 passivation of P b, which affects the defect's spin state. Sequential hydrogenation at 253–353°C and degassing treatments in high vacuum at 743–835°C allowed to vary the P b density in the range 5 × 10 10 < [P b] (1.14 ± 0.06) × 10 13 cm -2. With increasing [P b] fine structure doublets are clearly resolved. It is found that (1 1 1)Si/SiO 2 interfaces, dry thermally grown at ≈920°C, naturally comprise a *Si ≡ Si 3 defect density — passivated or not — of 1.14 × 10 13 cm -2. 相似文献
8.
We observed the NMR signal of low-pressure gas 129Xe by laser enhanced method on an MSL-400 NMR spectrometer and measured nuclear spin relaxations of 129Xe gas at various temperatures. The relaxation rate constant of 129Xe- 133Cs spin exchange was obtained as (6.8±0.5)×10 -16cm -3s -1. 相似文献
9.
The weak neutral current results in a parity-violating one-pion-exchange potential in nuclei. A search for this force has been carried out with the 1081 keV γ-radiation of 18F, which is expected to be circularly polarized. Excited 18F nuclei were produced with the 16O( 3He, p) 18F reaction and the γ-ray polarization was measured with a multiple transmission polarimeter system. The experimental result P = (− 1.0 ± 1.8) × 10 −3 is smaller than recent theoretical estimates. 相似文献
10.
The βγ circular polarization correlation of the 3 −(β − 621 keV)3 −(γ 1692)2 + cascade in 124Sb, the 4 +(β − 662)4 + (γ 796)2 + (γ 605)0 + in 13Z4Cs and the 6 +(β −529)6 + (γ 937)4 + (γ 885)2 + (γ 658)0 + in 110mAg have been studied by using a Compton effect polarimeter. The measured asymmetry parameters are 0.172±0.004, −0.0702 ±0.0024 and 0.0549±0.0013 respectively. 相似文献
11.
In-beam γ-ray transitions in 181Hg, the lightest odd-A Hg isotope known thus far, have been identified from fragment mass-γ and γ-γ coincidence measurements. Five prolate deformed rotational bands were placed in the level scheme. A decoupled band built on the strongly prolate deformed 1/2 −[521] ground state was observed up to 29/2 −. A 5/2 −[512] configuration is suggested for a pair of strongly coupled bands displaying no signature splitting. The other two bands are also signature partner bands. They are populated with the largest intensity and exhibit splitting. They have been associated with the mixed neutron i 13/2 orbitals and are proposed to decay to an i 13/2 isomeric state associated with an oblate state. 相似文献
12.
The γ-rays following the β-decay of 82Br have been investigated using a 220 mm 3 Ge(Li) detector, an anti-Compton NaI(Tl) spectrometer and a two-dimensional coincidence arrangement. The 82Br was produced by thermal neutron activation of ammonium bromide. The presence of eight, well-known and 11 weak γ-rays has been established. It has been shown through half-life measurements that the newly identified γ-rays belong to 82Br decay and that the high-energy peaks are not to summing effects. All the reported transitions have been incorporated in a level scheme of 82Kr by introducing levels at 0, 776, 1474, 1820, 1953, 2093, 2426, 2554, 2647 and 2828 keV. Limits on probable spin and parity values for the newly-introduced levels have been established. The level introduced at 2828 keV on the basis of a 1008–1043 keV γγ-coincidence must be fed by a weak β-branch of 82Br with an end-point energy of 263 keV and log ft of approximately 6.1. 相似文献
13.
The γ-rays following the decay of 88Rb have been studied with a 40 cm 3 Ge(Li) detector with the aim of resolving discrepancies in some recent determinations of the decay scheme of this isotope. The existence of a 1799 keV γ-ray has been confirmed and three new γ-rays with energies of 1218, 1295 and 1368 keV have been found. All of these results are in good agreement with a decay scheme recently proposed by Ragaini and Knight. 相似文献
14.
因其较高的核自旋极化度所提供的探测灵敏度,超极化 129Xe气体已被成功应用于动物和人体磁共振成像(MRI).但是,在超极化 129Xe的收集-升华过程中,多种因素会导致 129Xe核自旋弛豫,进而限制其应用范围.本文通过理论模型分析和实验测量,验证了温度、磁场、螺旋冷阱材质等对冷冻恢复过程中超极化 129Xe弛豫的影响;同时,测量了自动收集-升华装置的稳定性.研究结果表明,升华方式和冷阱材质对 129Xe极化度损耗的影响显著;自制收集-升华装置的自动化程度高、长时间稳定, 129Xe极化度的恢复率可达到85.6% ± 4.7%.本研究非常有助于提升超极化 129Xe在动物和人体MRI中的使用效率. 相似文献
15.
Measurements have been made of the β-γ circular-polarization correlation paramter A for the 273 keV β-branch in the decay of 59Fe. It has recently been established that each of the principal β-branches of 59Fe involves Δ J=0 and thus has a possible non-zero Fermi matrix element MF which can be determined from the ƒ t value and A. Previous β-γ (_CP) measurements on this nucleide have all employed the usual γ-ray scattering technique. This method is suitable for the 475 keV β-branch but does not produce an accurate measurement of the lower energy branch because of energy discrimination difficulties. A transmission polarimeter with γ-discrimination has been used in the present work to obtain clean data on the 273 keV β-1.29 MeV γ-cascade. Calibration with 60Co (1.33 MeV) and 28Al (1.79 MeV) yielded A = −0.154±0.023. This gives for the isospin impurity coefficient and the effective Coulomb matrix element of the 1.29 MeV state (1.1±1.4) × 10 −3 and 9±11 keV, respectively. 相似文献
16.
The A( e, e′K+) YX reaction has been investigated in Hall C at Jefferson Lab. Data were taken for Q2 ≈ 0.35 and 0.5 GeV 2 at a beam energy of 3.245 GeV for 3He, 4He. The missing mass spectra are fitted with Monte Carlo simulations including Λ, Σ 0, Σ − hyperon production. Models for quasifree production are compared to the data, excess yields close to threshold are attributed to FSI. Evidence for Λ-hypernuclear bound states is seen for 3,4He targets. 相似文献
17.
The energies and relative intensities of γ-rays following the β-decay of 78As (and 76As) to levels in 78Se (and 76Se) have been measured using an 8 cm 3 Ge(Li) spectrometer. The β-decay of 78As has been measured using a superconducting magnet beta-ray spectrometer with two 3 mm thick Si(Li) detectors. These data plus β-γ and γ-γ coincidence results have been used to construct a level scheme with 18 excited levels in 78Se. The half-life of 78As was measured to be 90.7±0.2 min. 相似文献
18.
A discrete superdeformed band is found in 146Gd. Lifetime measurements yield an average quadrupole moment of 12±2 e b. A band crossing corresponding to an alignment of ≈2
is observed at a rotational frequency of 0.65 MeV. A theoretical analysis suggests that the band has a π6 2v7 1 configuration with odd spins and odd parity. Arguments are given that the [651 1/2] and [642 5/2] single-particle states are involved in the band crossing. 相似文献
19.
We present photoluminescence spectra of La 2.7Lu 2.29Cr 0.01Ga 3O 12 and La 2.32Lu 2.59Cr 0.02Ga 3.07O 12 doped with Cr 3+ obtained at high hydrostatic pressure up to 220 kbar, applied in a diamond anvil cell at 20 K and room temperature. In both materials we have obtained a pressure-induced 4T 2– 2E electronic cross-over. On the basis of the low-temperature R line luminescence at pressures above 100 kbar we have distinguished two dominant Cr 3+ sites: and β, existing in both materials, and one minor site δ, that exists only in La 2.32Lu 2.59Cr 0.02Ga 3.07O 12. The pressure-induced shifts of the R 1, R 1β and R 1δ lines as well as the pressure shift of the broad band related to the 4T 2→ 4A 2 transition in both materials have been estimated. 相似文献
20.
We have investigated the structure evolution of the 124-134Xe isotopic chain in the framework of the proton-neutron interacting model IBM2. The positive parity spectra of the ground state, quasi-β and quasi-γ bands are reproduced well. The staggering in 124-130Xe are almost completely removed and the γ band agree well with the experiment data, even for the high-spin quasi-γ states. The key quantities of the collective structure evolution, including level energies, the B(E2) transition branching ratios, and the M1 excitations to 1 1+ mixer-symmetry states are analyzed by comparing with the experimental data. The parameters for representation of the O πν(6) and SU πν*(3) features in isotopes are examined. Both experimental data and theoretical results show that the shape phase transition of 124-134Xe isotopic chain is from the SU πν*(3) (triaxial rotation) to the U πν(5) (vibration motion) with a considerable constituent of the O πν(6) symmetry (γ-unstable rotation), where the shape phase transition rapidly takes place between the neutron number N = 76 and N = 78. 相似文献
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