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1.
The level schemes of 98, 99Ru were studied with the reactions 98Mo(α, 3nγ) and 98Mo(α, 4nγ) at Eα = 35 to 55 MeV, using a large variety of in-beam γ-ray detection techniques and conversion-electron measurements. A search for the 3? state was carried out with the reaction 98Ru(p, p′). The ground-state band of 98Ru was excited up to Jπ = (12)+ and a negative-parity band up to (15)?. New levels in 98Ru were found at Ex = 2285 (Jπ = 4+), 2435 (Jπ = (3?, 4+)), 2671, 3540, 4224, 4847, 4915 (Jπ = (12)+), 4989 (Jπ = (12+)), 5521 (Jπ = (13)?), 5889, 6591 (Jπ = (15)?), and 7621 keV. New unambiguous spin and parity assignments were made for the levels at Ex = 2014 and 3852 keV, as Jπ = 3+ and 9?, respectively. New levels in 99Ru were found at Ex = 1976, 2021 (Jπ = (152+)), 2393, 2401 (Jπ = (172+)), 2875 (π = (+)), 3037, 3201 (Jπ = (232)?), 3460 (J = (172)), 3484 (Jπ = (212+)), 3985, 4224 (Jπ = (272?)), and 5359 keV. The 1070 keV, Jπ = 112? level in 99Ru has a half-life of 2.8 ns. A strongly excited negative-parity band is built on this level. A positive-parity band based on the ground state was excited up to Jπ = (212+). The level schemes are well reproduced by the interacting boson model in the vibrational limit.  相似文献   

2.
Levels of 184W populated in the decay of 8.7 h 184Ta have been studied by a variety of experimental techniques. As a result of β and γ-ray energy and intensity determinations and extensive β-γ and γ-γ coincidence measurements, a detailed 184Ta decay scheme accommodating more than 99.5% of the decay intensity has been established. Intense β-ray groups of end-point energies 1165±26 and 1123±26 keV populate levels in 184W at 1699 and 1746 keV, which de-excite predominantly to the 8.3 μs isomeric level at 1285 keV, recently identified as the 12?[510]ν?112+ [615]ν Kπ = 5? band origin. The 1699 keV level also de-excites to members of a 12?[510]ν?72 [503]ν Kπ = 3+ band based at 1425 keV. New information about the properties of the γ-vibrational and K = 2 octupole bands in 184W is presented and the possible configurations of the levels directly populated in the β? decay are discussed. The configuration 72+[404]π ?32? [512]ν Kπ = 5? is indicated for the 184Ta ground state.  相似文献   

3.
Levels in 208At were populated in the 209Bi(α, 5n) reaction, and the subsequent radiation was studied using γ-spectroscopic methods including γ-ray excitation function and angular distribution, γγ(t) coincidence and γt measurements, as well as measurements of conversion electrons. The excited spectrum of 208At is found to consist of two almost disconnected parts which are proposed to originate from seniority-three proton and neutron cascades. Two isometric states are observed. A T12 = 45 ± 2 ns state at 1090 keV is proposed to have the main configuration πh92j20+vi?1132j?20+ and Jπ = 10?. A high-spin isomer with T12 = 1.5 ± 0.2 μs at 2276 keV is assigned to be the π(h292i132)292+vf?152j?20+Jπ = 16? state. Shell-model arguments are used to assign configurations to most of the observed levels. Transition rates are discussed.  相似文献   

4.
We have studied the Kππ system in the 14.3 GeV/c reactions K?p → K?π+π?p, K?pK0π?π0andK?pK0π+π?n. The data have been obtained from a 500 000 picture exposure of the CERN 2m HBC. The first two final states are dominated by Q-production in the Kππ system; there is also an L-signal at M (Kππ) ~ 1.75 GeV. The reaction cross sections are compared to K?p data at other energies. We discuss the Kππ mass dependence of the diffractive production slope. Evidence is presented for a Q?p versus Q+p differential cross section cross-over around |t| = 0.17 GeV2. A t-channel isospin analysis for the KNK1(890)πN channels in the Q-region shows that the I = 1 exchange amplitude is ? 10% of the dominant I = 0 exchange amplitude. The Kππ decay distributions indicate a predominant JP = 1+ state in the Q-region, and an important JP = 2? contribution in the L-region. We find neither s-channel nor t-channel helicity conservation at the meson vertex in the Q- or L-regions. The Kπ angular correlation moments within the Kππ diffractive system are characteristic of Kπ elastic scattering, suggesting a π-exchange Deck-type production mechanism. There is evidence for a Kf0 and κπ contribution (where κ is the JP(Kπ) = 0+ state) to the diffractive Kππ system. A fit to the K?π+π?and K0π?π0 Dalitz-plot distributions for the Q-re gion indicates that the ratio of K? to K1π decay amplitudes decreases with increasing Kππ mass.  相似文献   

5.
E. Hagn  E. Zech  G. Eska 《Nuclear Physics A》1981,361(2):355-367
The hyperfine splitting frequencies NBH.F./h of 2.7 h 93Tc (Jπ = 92+), 4.9 h 94Tc (Jπ = 7+) and 20 h 95Tc (Jπ = 92+) as dilute impurities in Fe have been measured with NMR on oriented nuclei as 336.36(5) MHz, 175.11(1) MHz and 315.97(2) MHz, respectively. From the resonance shifts with an external magnetic field B0 the hyperfine field of TcFe has been determined as -317(5) kG. Taking this into account the nuclear g-factors are deduced as g(93Tc) = 1.392(22), g(94Tc) = 0.725(11) and g(95Tc) = 1.308(21).  相似文献   

6.
Gamma rays following the β? decay of 30Al have been investigated with a Ge(Li) detector. The 30A1 sources were produced by fast neutron bombardment of an enriched 30Si sample. Evidence for two previously unreported β? branches has been deduced. The existence of allowed β? transitions to Jπ = 2+and 3+ states and to the Jπ = 4+ level at 5.95 MeV determines Jπ = 3 + for the 30Al ground state (T12 = 3.56 ± 0.02 s). These results are compared to a recent shell-model calculation.  相似文献   

7.
A complete set of conventional γ-ray spectroscopic techniques has been applied to investigate the level structure of 156Gd. A total of twenty-five new levels has been established; unambiguous spin assignments could be given for twelve of them on the basis of angular distributions and conversion electron measurements. The proposed level scheme contains 49 levels, which can be ordered in seven rotational bands. The ground-state band was excited up to Jπ = 14+, the β-band up to 10+, the γ-band up to (11+), the second Kπ = 0+ band tentatively up to (10+), the Kπ = 4+ band up to (8+). Two negative-parity bands, one with even spins and one with odd spins, were excited to Jπ = (12?) and (13?). An isomeric state was established with T12 = 1.3 μs, Jπ = 7?, Ex = 2137.7 keV. The properties of the Kπ = 4+ band and the isomeric state can be well explained by two-quasiparticle configurations. The negative-parity bands are interpreted as aligned octupole bands. Positive and negative-parity bands have been calculated in terms of the IBA model. Good agreement with the experimental results is obtained.  相似文献   

8.
The 169Tm(t, α)168Er reaction has been studied using 17 MeV polarized tritons from the Los Alamos National Laboratory tandem Van de Graaff accelerator. The α-spectra were analyzed with a Q3D magnetic spectrometer. The overall energy resolution was typically ~ 15 keV (FHWM) and angular distributions of cross sections and analyzing powers were obtained for levels up to ~ 2.7 MeV. The fact that spins and parities for all levels up to ? 2 MeV were previously known from an extensive series of (n, γ) studies made it possible to determine specific two-quasiproton structures for many bands from the present results. The Kπ = 2+ γ-vibrational band was found to have a large 32+ [411]p + 12+[411]p admixture, consistent with the predicted microscopic composition of this phonon, but no 52[413]p ? 12+ [411]p component was observed. The Kπ = 04+ band at 1833 keV has ~ 25% of the 12+ [411]p ? 12+[411]p two-quasiproton strength. This is in excellent agreement with the Soloviev model but is inconsistent with the interacting boson model, in which the Kπ = 04+ band is composed almost completely of multiphonon configurations that should not be populated in a single-nucleon transfer reaction. The Kπ = 4?, 72?[523]p + 12+ [411]p two-quasiproton and the Kπ = 4?, 72+[633]n + 12?[521]n two-quasineutron states are mixed strongly with each other, but the two Kπ = 3? bands composed of antiparallel couplings of the same particles are not. A good qualitative explanation of this mixing pattern is provided in terms of the effective neutron-proton interaction.  相似文献   

9.
E. Hagn  E. Zech 《Nuclear Physics A》1982,373(2):256-266
The magnetic hyperfine splitting vM=|gμNBHF/h| of 196mAu (jπ=12?; configuration ¦(π112(v132+)〉12?; T12 = 9.7 h) as dilute impurity in Ni has been determined with nuclear magnetic resonance on oriented nuclei as 96.0(2) MHz. With the known hyperfine field BHF = ?264.4(3.9) kG corrected for hyperfine anomalies the g-factor and magnetic moment of 196mAu are deduced to be |g| = 0.476(7) and |μ| = 5.72(8) μN. Taking into account the known magnetic properties of π12? and v132+ isomeric states in the neighbouring odd Pt, Au and Hg nuclei the structure of the 12? state is discussed.  相似文献   

10.
High-spin states in 38K are investigated with the 24Mg(16O, pnγ)38K reaction at E(16O) = 36–44 MeV. A recently developed Compton-suppression spectrometer with 120 msr solid angle and a pulsed beam are employed to study their γ-decay. For the E4 transition from the isomeric level at Ex = 3458 keV to the ground state a branching ratio of (0.15 ± 0.02)% is found. On the basis of angular distribution and polarization measurements, in which the delayed feeding component is eliminated, spin-parity assignments are obtained of Jπ(2646 keV) = (2, 4)?, Jπ(3420 keV) = (4, 6)? and Jπ(3458 keV) = (5, 7)+. Prompt-delayed and prompt γγ coincidence experiments are performed to locate high-spin levels above the isomer. Hitherto unobserved levels of high spin are found at Ex = 5254, 7397, 8693, 8747 and 10980 keV and assignments of Jπ = (9+), (10?), (12?), (11?) and (13?) respectively, are suggested by weak-coupling considerations. The experimental results are compared with a large-scale shell-model calculation performed in a configuration space with a 28Si core and ten active particles distributed over the (2s12, 1d32, 1f72, 2p32) shells. The high-spin states appear to have a rather simple shell-model structure.  相似文献   

11.
In the 48Ca (τ,α)47Ca reaction at 25 MeV, some angular distributions are well reproduced by CCBA calculations, assumping double-step excitation of [48Ca1?f72?1] states. Unambigous Jπ assignments are extracted from the analysis.  相似文献   

12.
13.
A simultaneous analysis of low-energy (W ? 2 GeV) data for the reactions π?p→ KOΛ and K?p → πOΛ has been made using the hypothesis of two-component duality combined with fixed-t dispersion relations. Results are presented for the ?1 Λπ and N1 ΛK couplings. The low-energy amplitudes are used to evaluate FESR integrals and lead to large EXD breaking for the KV1 ? KT1 helicity flip amplitudes.  相似文献   

14.
Resonances in the reaction 56Fe(p, γ)57Co have been surveyed over the energy range 1.2 ? Ep ? 1.5 MeV wherein the analogues of the ground state (Jπ = 12?, 0.014 MeV state (Jπ = 32?) and 0.136 MeV state (Jπ = 52?) of 57Fe are expected to occur. Gamma-ray angular distributions have been used to establish resonance and bound-state spins, and decay schemes have been determined. The analogue resonances appear to be severely fragmented, however the density of resonances of a given spin correlates quite well with (3He, d) results and with the expected analogue-state positions.  相似文献   

15.
The nature of mesons in the 0++ nonet is studied. In particular we discuss the parameterization of the I = 0 S wave in terms of the S1 and possible ? mesons. The S1 parameters are determined by fitting to π?π+ and K?K+ production data. In particular we find (gKKS1gππS1)2 = 4.0 ± 0.6.  相似文献   

16.
The characteristics of the decay sequences 12ΛB → π? + 12C1, 12C1 → 3α are discussed for the two sharp levels of 12C1 at excitation energies of 12.7 MeV (Jf = 1+, T = 0) and 16.11 MeV (Jf = 2+, T = 1), which are observed prominently in this decay process. The transition rates for these processes and the angular correlations in the final four-particle state αααπ? are discussed quantitatively, using the intermediate coupling model for both the 12ΛB and 12C1 systems, as a function of the 12ΛB spin J. Three distinct tests are proposed, which are sensitive to the spin J for ground-state 12ΛB, and which have been used by the European K? Collaboration to deduce that J = 1 for 12ΛB. The implications of this conclusion for the ΛN and ΛNN interactions are briefly discussed.  相似文献   

17.
The branching ratio Λ(KS0→π+π?γ)Λ(KS0→π+π?) has been determined to be (2.68±0.15)×10?3 for photon energies Eγ1 greater than 50 MeV in the KS0 rest frame. The decay KS0π+π?γ is found to be dominated by the internal bremsstrahlung transition. The branching rato of a possible direct transition is found to be less than 0.06 × 10?3 at 90% confidence level for Eγ1 > 50 MeV.  相似文献   

18.
We discuss the structure of the momentum transfer distributions for the diffractive dissociation processes p → nπ+, p → Δ++π? and K?K89010π?. In the near-threshold mass region a clear break of slope is found around t′KK ~ 0.25 GeV2 for the two baryonic channels, whereas no comparable structure is seen for the mesonic system. The KK1π differential cross section exhibits a nearly exponential behaviour up to tpp ~ 0.6 GeV2, falling over three orders of magnitude. The slope variations and breaks are strongly correlated both to the mass region considered and to the decay angle of the fragmentation system.  相似文献   

19.
The reaction π?p→K+K?n has been studied on a hydrogen target (27 000 events) at 18.4 GeV/c and on a polarized target (54 000 events) at 17.2 GeV/c. A combination of results of both experiments allows a partial-wave analysis of the K+K? system between 1.1 and 1.74 GeV mass without any model assumptions. In general our fits yield unique solutions. Using results of our previous analysis of π+π? final states and assuming the dominance of the positive G-parity states in the K+K? system, the branching ratios BR(KK/ππ) of partial waves into KKand ππ are determined. The S-wave appears to be mainly a broad ε (1300) with BR(K K/ππ) = 0.068?0.021+0.017. The weak P-wave can be described by a tail of the ?(770) with BR(K K/ππ) = 0.081?0.025+0.029. The D-wave is interpreted in terms of a superposition of f(1270) + A2(1310) + f′(1515) resonances. The fit yields BR(K K/ππ) = 0.069?0.031+0.023 for the f(1270) and BR(ππ/all) = 0.027?0.013+0.071 for the f′(1515). The F-wave shows the g(1690) meson with BR(K K/ππ) = 0.191?0.037+0.040. All the above values refer to the t bin between 0.01 and 0.20 (GeV/c)2. Some results are also given for the high-t region.  相似文献   

20.
The 91Zr(d, 3He) reaction was studied at a deuteron energy of 28 MeV. Angular distributions were measured from 13° to 47°; lp values were extracted for the prominent lines of 90Y. The lp values and transition strengths were determined by DWBA analysis. The angular distributions for the p12)(νd52) doublet (g.s. and 0.20 MeV state) exhibit the characteristic l = 1 shape. States at 1.42, 1.57, 1.64 and 1.81 MeV were also populated strongly in the (d, 3He) reaction; the 1.42, 1.57 and 1.81 MeV levels contain l= 1 transition strength and are most likely members of the p32?1)(νd52) multiplet. The 2.03 MeV state has a characteristic l = 3 angular distribution and is suggested to be the only member of the f32?1)(νd52) sextet to be unambiguously observed in this study, most probably the 5? or 4? member. The members of the g52)(νd92) sextet were populated weakly (less than 100 μb/sr) in this reaction.  相似文献   

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