共查询到20条相似文献,搜索用时 796 毫秒
1.
S.I. Hayakawa S.K. Mark J.K. Lee J.E. Kitching G.C. Ball W.G. Davies 《Nuclear Physics A》1973,199(3):560-570
States in 92Tc have been studied by means of the 92Mo(3He, t) reaction at 27.5 MeV. The Q-value for this reaction and the excitation energy of the isobaric ground state analogue of 92Mo were determined to be ?7.882 ± 0.030 MeV and 3.813 ± 0.030 MeV respectively. Strongly populated levels in 92Tc appear to belong to configurations arising from the multiplet. 相似文献
2.
The (d, 3He) and (α, t) proton transfer reactions on 91Zr were studied at incident energies of 24.3 and 35.4 MeV, respectively. Angular distributions were measured from 6° to 50° (90Y) and 60° (92Nb). High detection efficiency and good energy resolution were obtained by using a magnetic spectrograph in connection with a multiwire proportional chamber. For the low-lying multiplet levels in both nuclei angular momentum transfers and spectroscopic factors were determined by DWBA analysis. In 92Nb the states at 0, 0.135, 0.29, 0.36 and the sum of the states at 0.48 and 0.50 MeV show typical l = 4 shapes. They belong to the ()() sextet. The corresponding multiplet in 90Y is weakly populated (), and l = 4 shapes are found for the levels at 0.68, 0.78, 0.95, 1.05 and 1.30 MeV proving previous assignments. The members of the low-lying ()() doublets in 90Y and 92Nb exhibit a characteristic l = 1 angular shape. The levels at 1.42, 1.57, 1.64, 1.76 and 1.81 MeV in 90Y are excited both by l = 1 and l = 3 resulting from a strong mixing of the ()?1() and () multiplets. Only the level at 2.03 MeV displays a pure l = 3 shape. From the spectroscopic information on the ()() and ()() multiplets in 90Y and 92Nb the g.s. configuration mixing in 91Zr is deduced. 相似文献
3.
S. Gilad S. Cochavi M.A. Moinester J. Alster M. Buenerd P. Martin 《Nuclear Physics A》1974,233(1):81-90
The hole-hole structure of 94Y was studied via the reaction 96Zr(d, α)94Y and compared to the particle-hole structure of 90Y, which was populated by the reaction 92Zr(d, α)90Y. The deuteron beam energy was 28 MeV. Angular distributions of both reactions were obtained for the prominent lines. New states of 94Y were observed at 0.44, 1.17, 1.39, 1.53, 1.82, 1.90, 2.17, 2.33, 2.46 and 2.77 MeV. Our data are consistent with the previously reported 2? assignment of the ground state, and we suggest Jπ = 3? for the 0.44 MeV state, these being members of the doublet. The 1.17 state is suggested to be a member of the multiplet. The Q-value of the 96Zr(d, α)94Y reaction was measured to be 7.609 ± 0.020 MeV. The reaction 94Zr(d, α) was performed at two angles. Several new states of 92Y were observed at 0.31, 0.78, 1.03, 1.31, 1.49, 1.69 and 1.89 MeV. 相似文献
4.
Energy levels in 42Ca up to 7.8 MeV have been studied in the neutron capture reaction 41Ca(d, p)42Ca with 12 MeV bombarding energy. Ninety-four excited states have been identified and angular distributions have been measured in the interval from 5° to 110° by means of a broad-range magnetic spectrograph. The angular distributions together with DW calculations have been used to determine In values and spectroscopic factors. The strength sum agrees with shell-model expectations if the f spectroscopic factors are renormalized by , in line with other . transfer experiments on 40Ca and 41Ca. A similar renormalization of the ln = 1 spectroscopic factors brings this strength sum in accordance with the shell-model calculations. The effective () matrix elements for 42Ca are compared with the corresponding matrix elements of 42Sc and 48Sc. The differences between the three sets of matrix elements are of the order of a few hundred keV or less. The monopole centroid energy of the ( multiplet is shifted downwards in the mass-42 nuclei compared to 48Sc, possibly indicating the importance of the monopole pairing force near 40Ca. 相似文献
5.
S. Cochavi S. Gilad M.A. Moinester J. Alster M. Buenerd P. Martin 《Nuclear Physics A》1974,233(1):73-80
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 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 multiplet. The 2.03 MeV state has a characteristic l = 3 angular distribution and is suggested to be the only member of the sextet to be unambiguously observed in this study, most probably the 5? or 4? member. The members of the sextet were populated weakly (less than 100 μb/sr) in this reaction. 相似文献
6.
Differential cross sections for neutrons scattered from 11B have been measured for 2.2 MeV < En < 4.5 MeV. The differential cross section σ(θ) is fitted reasonably well by R-matrix parameters for broad states in 12B with assignments 1 ? and (1) + at excitation energies Ex = 5.8 and 6.8 MeV respectively. The broad 1 ? state has not been previously observed and is believed to be the 1 ? member of the particle-hole multiplet predicted to exist by earlier shell model calculations. Its existence completes the identification of all of the levels of this multiplet (3 ?, 2 ?, 4 ?, 1 ?). The broad (1)+ level at Ex = 6.8 MeV has not been previously observed. States at excitation energies Ex = 5.61, 5.73 and 6.6 MeV have been assigned spins and parities of 3+, 3? and (1)+ respectively. These states had previously been assigned spins of 2, 3 and respectively. Work on T = 1 states in 12C1 has been compared with the present work. 相似文献
7.
92, 94Nb and 94, 96, 98Tc have been produced by the (p, n) reaction at proton energies on and near the isobaric analog resonance. 95,97Tc have been produced by the (p, γ) reaction below the (p, n) threshold. Internal conversion electrons due to the decay of their excited states were detected on-line with a mini-orange spectrometer which is optimized for the energy range 50 to 500 keV. Gamma rays from these nuclei were detected with a thin Ge(Li) detector. Isomeric-delayed internal conversion electrons and γ-rays were observed, using a nanosecond-pulsed beam. The internal conversion coefficients for 55 transitions in these nuclei have been determined and their multipolarities deduced. The multipolarity of the transitions in these nuclei is predominantly M1. Negative parities have been assigned through use of the isobaric analog resonance enhancements of the population of negative-parity final states. The systematic behavior of the 2?, 3? doublet and of the multiplet in these nuclei is discussed. 相似文献
8.
P. de Gelder D. de Frenne E. Jacobs H. Thierens A. de Clercq P. Dhondt K. Heyde A.J. Deruytter G. Tittel N. Kaffrell N. Trautmann F. Schussler 《Nuclear Physics A》1980,337(2):285-300
The 102Mo activity was obtained by photofission of natural U and thermal-neutron induced fission of 235U, with subsequent chemical separation of the molybdenum fraction. In addition, nuclei with mass 102 were separated from fission products of 235U(nth, f) using the mass separator LOHENGRIN. A decay scheme and absolute γ-intensities are deduced from measured γ-ray, X-ray and γ-coincidence spectra. Logftvalues are calculated. Shell-model calculations for a multiplet have been carried out using effective nucleon-nucleon interactions. The γ-decay between low-lying, low-spin members of this multiplet was studied in detail and compared with the experimental data. 相似文献
9.
Energy levels in 50V up to 4.3 MeV have been studied using the 49Ti(3He, d)50V and 51V(d,t)50V reactions with 3He particles of 22 MeV and deuterons of 19.5 MeV incident energy. More than eighty levels are seen, with angular distributions taken for forty-one levels in the (3He, d) reaction and for the ten lowest levels in the (d, t) reaction. The angular distributions are compared with the distorted-wave Born approximation (DWBA) to extract the l-values of the transferred nucleons and obtain the spectroscopic strengths. In the stripping reaction, a small amount of l = 0 and l = 2 strength is seen, indicating the presence of s and d proton holes in the g.s. of 49Ti. The results are compared with a recent shell-model calculation based on an configuration, and show qualitative agreement. 相似文献
10.
The nucleus 11B has been studied over the excitation energy range from 8.5 MeV to 21.5 MeV with the 9Be(3He, p)11B / reaction at / E3He = 38 MeV. The analogs of the parent states in 11Be have been located at 12.56, 12.92, 14.40, 16.44, 17.69, 18.0, 19.15 and 21.27 MeV. A complementary measurement with the 9Be(α, d)11B reaction at Eα = 48 MeV demonstrates that the 16.44, 17.69, 18.0 and 19.15 MeV resonances have rather pure isospin . The 14.40 MeV state is a strongly isospin-mixed analog of the state in 11Be. It is argued that spin S = 1 transfer is involved in the excitation of the 16.44 MeV state and its 3.887 MeV parent in 11Be in a two-step stripping process. The states and the lowest three states are compared with the predictions of DWBA utilizing shell-model form factors. It is concluded that the strength is more strongly fragmented than is implied by the calculations of Teeters and Kurath. 相似文献
11.
The structure of 92Nb has been investigated using the 33.8 MeV 92Zr(3He, t) and (3He, p2nγ) reactions. Several previously unobserved levels, including several belonging to the multiplet, are reported. The results are discussed in terms of the shell model. 相似文献
12.
A distorted wave analysis of the 32S(t,p) 34S reaction reveals that the 0+ state at 5.86 MeV, the 2+ state at 7.80 MeV and the 4+ state at 8.42 MeV are the principal components of the , T = 1 multiplet. 相似文献
13.
D. Cline M.J.A. De Voigt P.B. Vold Ole Hansen O. Nathan D. Sinclair 《Nuclear Physics A》1974,233(1):91-104
Energy levels in 40Ca up to 10.2 MeV have been studied in the neutron pickup reaction 41Ca(τ, α)40Ca with 20 MeV bombarding energy. Thirty excited states have been identified and angular distributions have been measured in the interval from 5° to 40° by means of a split-pole magnetic spectrometer. The angular distributions together with DW calculations have been used to extract ln values and spectroscopic factors. The ln = 2 strength distribution for the particle-hole levels is compared to the lp = 3 strength distribution from pr stripping data. 相似文献
14.
The reaction 12C(7Li, t)16O has been studied at with the LASL tandem accelerator and QDDD magnetic spectrometer. Angular distributions to levels with Ex < 11 MeV have been obtained from 0° to 90°, including 0°. The results have been analyzed with finite-range distorted-wave Born approximation theory. The α-particle spectroscopic factors and reduced widths obtained are compared with those calculated with group theory (SU(3)) and other models. The analysis of data for the 7.1 and 9.6 MeV Jπ = 1? levels, which are of great importance in stellar helium buring, yields a ratio, R, of dimensionless reduced α-widths . The observed line width of the 9.6 MeV level (Γc.m. = 390 ± 60 keV) is less than the accepted value (Γc.m. = 510 ± 60 keV) and implies θ2a(9.6 MeV) ≈ 0.6. These results as well as data for the 6.92 MeV Jπ = 2+ and 10.35 MeV Jπ = 4+ “α-cluster” states indicate 0.09 < θ2a(7.1 MeV) < 0.33 with a mean value θ2a(7.1 MeV) = 0.14 ± 0.04. The implication for stellar helium burning is discussed. 相似文献
15.
Differential cross sections were measured for 50Ti(p, p) at four angles for Ep = 1.83 to 2.97 MeV, with an overall energy resolution of about 350 eV. Spins, parities and total widths were extracted for 212 levels. An energy region near Ep = 1.37 MeV was also examined in order to study the analogue of the ground state of 5Ti. Coulomb energies and spectroscopic factors were determined for the analogues of the ground and first excited states of 51Ti. The latter analogue was highly fragmented. The s-wave spacing and width distributions were analyzed and the number of missing levels estimated. The and proton strength functions were determined. 相似文献
16.
The 42Ca(α, 3He)43Ca reaction has been studied at 36 MeV incident energy. Angular distributions have been measured from 4° to 42° using a split-pole spectrometer and position sensitive Si detectors, for about 40 levels located up to 6 MeV excitation energy. A local zero-range DWBA analysis has been carried out; l = 3 and 4 assignments are tentatively proposed for levels located above 4 MeV excitation energy, indicating a strong fragmentation of the strength between 4 and 6 MeV and the location of the main component of the strength above 6 MeV. A number of weakly excited levels cannot be reproduced by DWBA analysis. Their angular distributions have been compared with the results of coupled-reaction-channel calculations assuming two-step excitation of weak coupling states with a [42Ca1 ? structure. A reasonable agreement has been obtained, confirming that the two-step process cannot be neglected in the analysis of the (α, 3he) reaction. 相似文献
17.
The 96Mo(p, n) and 96Mo(p, nγ) reactions have been studied for proton energies between 3.8 and 5.5 MeV. Energy levels in 96Tc up to 632 keV excitation energy have been determined. Possible spin and parity assignments are given for several levels based on the neutron enhancement and angular distributions observed on and off resonance of the isobaric analog state in 97Tc, as well as the observed γ-yields. The first excited state reported at 34 keV was found to be a close doublet only 0.8 keV apart. The observation of this doublet in the (p, n) reaction was used to determine the ground state Q-value Q = ? 3.760±0.010 MeV. 相似文献
18.
The results of high-resolution studies of the 91Zr(d, p) reaction at Ed = 12 MeV and the 90Zr(t, p) reaction at Et = 11.85 MeV are presented. Absolute cross sections have been measured for both reactions and (d, p) spectroscopic factors determined. A comparison of these results with earlier data has been made, and although many of the previous assignments have been confirmed, many new features concerning the structure of 92Zr have been discovered. Shell-model calculations have been performed for 91Zr and 92Zr using a neutron space which includes the , , , and orbits and a proton space comprising the and orbits. Realistic proton-neutron and neutron-neutron interactions based on the Sussex matrix elements were used in the calculations. Spectroscopic factors have been calculated for the 90Zr(d, p) and 91Zr(d, p) reactions and cross sections calculated for the 90Zr(t, p) reaction. In general, good agreement between the theoretical and the experimental results has been obtained. 相似文献
19.
The doubly odd nucleus 140Pr has been investigated by means of the 141Pr(d, t)140Pr and 140Ce(p, nγ)140Pr reactions. Twenty-eight levels, up to 1300 keV excitation, were observed in the pickup study. DWBA analysis was used to determine l-values and spectroscopic factors for all but a few which are very weakly populated. Gamma-ray angular distributions, measured at Ep = 4.78 MeV for the five strongest γ-rays, show appreciable nuclear alignment and demonstrate the feasibility of such experiments in this mass region. Taken together, the two studies have permitted the identification of the 12 levels expected from the low-lying (), (), () and (π1gν3s?1) configurations. Tenta assignments for the strong odd-parity states are suggested on the basis of their spectroscopic factors. 相似文献
20.
E. Hammarén E. Liukkonen M. Piiparinen J. Kownacki Z. Sujkowski Th. Lindblad H. Ryde 《Nuclear Physics A》1979,321(1):71-108
The 146, 148Nd(α, χn) and 148, 150Nd(3He, χn) reactions at Eα = 20–43 MeV and E3He = 19–27 MeV, are used to study excited states in the 149Sm86 and 149Sm87 nucleides and consequently the low-spin odd-parity excitation. The mixing ratios and multipolarities of the most prominent transitions are deduced from the combined evidence of angular distribution and electron conversion data. The spin-parity assignments for most of the levels observed are established. In 148Sm the ground state band extending to Iπ = 10+ is predominantly populated. A negative-parity odd-spin band extending from Iπ = 3?through 11? is also observed. The bands in 148Sm are interpreted within the framework of the interacting boson approximation model. In 149Sm positive-parity levels with spin up to and negative-parity levels with spins up to are observed. The predominant γ-decay proceeds via transitions associated with , , and intrinsic configurations. The branching ratios B(E1)/B(E2) are calculated and compared in both 148Sm and 149Sm nucleides. The B(E1)/B(E2) dependence on the value of Z for some N = 86 (as well as 88 and 84) isotones showing a minimum of Z = 64 was noted. A 4 ns high-spin isomer mainly decaying into the positive-parity band based on the state in 149Sm is found. Experimental evidence is presented to interprete the , , … and , , …, ΔI = 2, sequences in 149Sm as arising from the coupling of an neutron to the octupole and quadrupole modes of the 148Sm core nucleus. The absolute reaction cross sections for the 146, 148, 150Nd(3He, χn) reactions have been determined for different bombarding energies. The mixing of the and shells is discussed in the framework of an axial-particle-rotor model calculation. 相似文献