共查询到20条相似文献,搜索用时 15 毫秒
1.
J. Recht Y.K. Agarwal K.P. Blume M. Guttormsen H. Hübel H. Kluge K.H. Maier A. Maj N. Roy D.J. Decman J. Dudek W. Nazarewicz 《Nuclear Physics A》1985,440(2):366-396
High-spin states in 169, 170W have been populated in reactions. In-beam γ-ray spectroscopic techniques with multi-detector set-ups, multiplicity filters and an anti-Compton shield have been used. Levels up to about spin 30 (tentatively up to 36) in 170W and up to (tentatively up to ) in 169W have been identified. The data are interpreted within the framework of a pairing-selfconsistent cranking model. The nuclear shape evolution with increasing spin is studied theoretically within a configuration-controlled shell correction approach and also pairing effects are studied. The behaviour of the yrast states around 28+ in 170W can be related in a model-dependent way to a reduction of the neutron-pairing correlations. 相似文献
2.
Rotational sidebands in 166Er were observed using the 24 MeV 164Dy(α, 2nγ) reactions. The ground-state band was observed up to spin 16+ and does not backbend. A strong backbend is, however, observed in a Kπ = (O+) sideband, indicating that the 12+ state of the previously unknown S-band is at 2656 keV. The γ-band shows significant rotational alignment above I = 10+. Levels of at least two negative-parity bands, one of which is primarily the Kπ = 2? octupole vibration, are also observed. 相似文献
3.
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
4.
The decay of the photo resonances in 14N and 14C nuclei is analyzed in terms of the shell model with intermediate coupling. Cross sections and branching ratios of nucleon channels are compared with experimental data. Successive decay branches are estimated. 相似文献
5.
The interaction of 63Cu ions with 197Au nuclei have been studied experimentally at incident energies of 365 and 443 MeV (1.1 and 1.4 times the Coulomb barrier). Mass and kinetic energy distributions of reaction products have been measured at several angles. Near the grazing angle, a continuous transition was found from elastic events to partially damped (PD) events, and to fully damped events (quasi-fission, QF). Away from the grazing angle a clean separation between elastic and QF events was observed. Events that may be due to fission following fusion (CF) were also obtained. Results are discussed in terms of decomposition into PD, QF, and CF components. The QF kinetic energy is independent of the incident energy (implying full damping of the initial relative motion). It is lower than the Coulomb barrier and close to the kinetic energies from the fission of similar systems. The angular distribution is peaked somewhat forward of the grazing angle for low mass transfers. For large mass transfers the yield increases slowly with decreasing angle. At 443 MeV a large contribution from negative angles is present. σQF accounts for more than 65 % of the reaction cross section σR at 443 MeV and for more than 50 % at 365 MeV. The upper limit on CF is about 10 % of σR, and σPDis of the order of 25 % of σR. 相似文献
6.
Anomalous results obtained in recent electron-nucleus scattering experiments suggest that a dispersion correction may contribute significantly to elastic cross sections in the region of the first diffraction minimum. Such a dispersion correction describes the effect of possible virtual nuclear excitations neglected in the conventional phase-shift analyses of electron scattering data. To investigate these effects, the Yale University electron accelerator has been used to study the scattering from 184W and 186W at incident energies between 40 and 65 MeV and scattering angles between 70° and 150°. No evidence of a dispersion effect is seen in the nucleus 186W. In the case of 184W, a comparison of the measured cross sections with those expected on the basis of the results of muonic X-ray experiments indicates that any dispersive effect is limited to less than 10% in the region of the first diffraction minimum. A summary of the results of this laboratory's search for dispersion effects in Nd, Sm, and W is appended. 相似文献
7.
T. Motobayashi H. Ejiri T. Shibata K. Okada M. Sasao K. Maeda H. Suzuki A. Shimizu H. Sakai 《Nuclear Physics A》1984,413(2):290-310
The projectile breakup process for 100 MeV 3He interacting with 165Ho and 166, 167Er nuclei was studied by measuring singles and coincidence spectra of the breakup fragments and following γ-rays. By comparing the data of the 3He-induced reaction with those of the α-induced reaction, the breakup process was found to make a large contribution to the charged-particle spectra of the 3He-induced reaction. Contributions of the elastic breakup, inelastic breakup, and breakup fusion processes were deduced individually from the particle-γ coincidence measurements. 相似文献
8.
Excited states in the neutron-deficient nucleus 168W, populated in the 148Sm(24Mg, 4n)168W reaction, have been studied using γ-ray spectroscopy. The yrast band, which is identified up to about spin 28, shows a very strong backbend at low frequency, , attributed to the neutron alignment. Evidence for a second backbend is also observed. A strongly populated odd-spin (probably negative-parity) sideband is also identified to the spin, and shows several band-crossing anomalies. The characterisation of the anomalies is made by comparison with CSM calculations. Proton and neutron alignments are probably present in the sideband, and the second backbend in the yrast sequence may be due to alignment of protons. 相似文献
9.
L. Głowacka M. Jaskóła J. Turkiewicz L. Zemło M. Kozłowski W. Osakiewicz 《Nuclear Physics A》1977,284(2):257-263
The energy spectra of α-particles emitted in the 161Dy(n, α)161Gd and 163Dy(n,α)160Gd reactions have been measured at neutron energies equal to 14.1 and 18.2 MeV. The results have been analysed in terms of Hauser-Feshbach, pre-equilibrium and knock-on models. The experimental data can be described assuming the existence of preformed α-clusters in target nuclei and the processes involving only few degrees of freedom. 相似文献
10.
D. Konnerth W. Trombik K.G. Bernhardt K.A. Eberhard R. Singh A. Strzalkowski W. Trautmann 《Nuclear Physics A》1985,436(3):538-560
We have studied elastic scattering, inelastic scattering and several transfer channels of the systems 14C + 14C and 14C + 12C over a wide range of energies up to Ec.m. = 35 eMeV and 32 MeV, respectively. The reaction channels were identified by means of kinematic coincidences between solid-state detectors, γγ coincidences were measured to determine cross sections for mutual inelastic scattering of 14C + 14C.Pronounced regular gross structures, similar to those found for 16O + 16O, are observed in the elastic excitation function of 14C + 14C at θc.m. = 90°, The angular distributions measured at the energies of the maxima and an optical-model analysis suggest that one or a few surface partial waves dominate the scattering behaviour. Correlated structure of narrower width is found in the inelastic channels and, to a lesser degree, in the transfer channels which appear with rather small cross sections.In 14C + 12C elastic scattering the gross structures are strongly fragmented, in contrast to 14C + 14C but similar to 12C + 12C. While the 12C(2+) excitation is very weak, the observed strengths of the 14C(3?) excitation and of neutron transfer point to a substantial role of these channels as coupling partners to the elastic configuration and to their influence on the elastic scattering behaviour. A correlated intermediate structure is observed near 23.5 MeV, where a dominance of l = 18 is suggested by the elastic scattering angular distribution. This unexpectedly high l-value exceeds lgraz at this energy by at least two units of ?. 相似文献
11.
The differential cross sections at 90° for the 51V(e, p0)50Ti and 52Cr(e, p0 + p1)51V reactions have been measured over the giant dipole resonance region. These cross sections were used to obtain the differential cross sections of the 51V(γ, p0)50Ti and 52Cr(γ, p0 + p1)51V reactions. The results show two peaks that appear at the same energies as the main peaks of the (γ, n) and (γ, p) cross section for both nuclei. The angular distributions of protons from the (e, p) reaction have also been measured at several points of the incident electron energy. The coefficients A2 obtained by fitting with a series of Legendre polynomials, W(θ) = 1 + A1P1(cos θ)+A2P2(cos θ), varies with excitation energy. These results are discussed in terms of the direct-semidirect process considering isospin effects in the giant dipole resonance. 相似文献
12.
Fusion and inelastic scattering coupled-channel calculations are carried out for the systems 18O + 44Ca and 12C + 48Ti. Comparison between 12C + 48Ti and 32S + 24Mg sub-barrier fusion cross-section enhancement is made using simple analytical expressions. The distribution of the angular momentum absorbed by the compound nucleus is discussed in a quantum-mechanical coupled-channel model. 相似文献
13.
J. Nurzynski T.R. Ophel P.D. Clark J.S. Eck D.F. Hebbard D.C. Weisser B.A. Robson R. Smith 《Nuclear Physics A》1981,363(1):253-268
Excitation functions for the reaction 24Mg(16O, 12C)28Si(g.s., 2+1) were measured at 5°(lab) in the energy range 32 < Ec.m. < 49 MeV. Although the resonant structure, previously observed at lower energies, becomes progressively weaker, three new correlated maxima have been observed near Ec.m. = 37.5, 40.2 and 43.5 MeV. Angular distribution measurements at these energies yield spin assignments, from P2j(cos θ) comparisons, of 27, 29 and 31, respectively. Attempts to find a consistent optical-model fit to the elastic scattering in the entrance channel and an exact finite-range DWBA fit to the four-nucleon transfer reaction in this energy range were unsuccessful. Such a failure is to be expected if strong couplings between the elastic channel and inelastic channels of either the initial or final system are important. The features of the resonance phenomena in the transfer reaction are discussed within a band crossing model framework. 相似文献
14.
Angular distributions of tritons from the 6Li(n, t)4He reaction were measured at En = 7.25, 6.77, 6.57, 5.24 and 4.71 MeV. Angular distributions of douterons from respectively, the 6Li(n, d)5He two-body breakup reaction were measured at En = 6.77 and 6.57 MeV, and of protons from the 6Li(n, p)6He reaction at En = 6.77, 5.24 and 4.71 MeV. All these reactions in 6Li were analyzed as direct interaction in the formalism of the distorted wave Born approximation. The optical model for the nuclear interaction was found to apply reasonably well to nuclei as light as 4He, 5He, 6He and 6Li. In addition, 6Li as an alpha-deuteron cluster gives the best bound-state wave function to describe the experimental angular distribution of tritons. The excitation functions at forward angles of the 6Li(n, t)4He, 6Li(n, d)5He and 6Li(n, p)6He reactions were measured for incident neutron energies between 4.4 and 7.3 MeV. It is found that the 6Li(n, d)5He two-body breakup reaction has a threshold at about En = 5.3 MeV. Angular distributions at En = 18.3 MeV for tritons and protons from the 9Be(n, t)7Li and 9Be(n, p)9Li, respectively, were also measured. 相似文献
15.
F.E. Cecil R.E. Anderson S.A. Durrance R.J. Peterson H.H. Wieman 《Nuclear Physics A》1981,370(2):277-283
The reaction 14C(3He, n)16O has been measured at a 3He bombarding energy of 25.4 MeV. The zero-degree differential cross section for the excitation of the three low lying 0+T = 0 states, at energies 0.0, 6.05 and 12.05 MeV are, respectively, 1.33 ± 0.10, 0.49 ± 0.10, and 0.50 ± 0.10 mb/sr These measured cross sections are in rough agreement with single-step zero-range DWBA calculations using an empirically determined 14C ground state wave function and in which the Brown and Green coexistence-model wave functions are used to describe the 16O 0+ states. The angular distribution of the transition to the ground state is measured between 0° and 32°. 相似文献
16.
D. Evers C. Ley E. Spindler W. Assmann K. Rudolph P. Konrad P. Sperr 《Nuclear Physics A》1977,275(2):363-380
The (3He, n) reaction on 16O and 18O has been used to study low-spin states in 18Ne and 20Ne up to Ex ≈ 8 and 20 MeV, respectively. The measured neutron angular distributions have been analysed using DWBA. By a comparison with shell-model calculations in the (s, d) shell it is found that most of the two-proton transfer strength can be explained within that shell. Important contributions, however, from the (f, p) shell in low-lying negative parity states are also present. 相似文献
17.
F. Todd Baker Alan Scott T.P. Cleary J.L.C. Ford E.E. Gross D.C. Hensley 《Nuclear Physics A》1979,321(1):222-230
Elastic and inelastic scattering differential cross sections for the 194Pt(12C, 12C′) reaction at a bombarding energy of 78 MeV have been measured. Data have been obtained for 0+, 2+, 4+, and 2+′, states in 194Pt. The data have been analyzed using a rigid asymmetric-rotor model in coupled-channels reaction calculations. It is found that satisfactory fits to all data can be obtained but only if the hexadecapole deformation is included in the asymmetric-rotor model. 相似文献
18.
The 20Ne(3He, n) reaction leading to the ground state of 22Mg has been investigated in the 3He+ energy range of 2.6 to 4.0 MeV. Angular distributions were determined with a neutron time-of-flight spectrometer at average incident energies (lab) of 3.27, 3.69, and 4.01 MeV between 0° and 120° (lab). Excitation functions for the energy region were measured at 0° and 80° (lab). The observed differential cross sections are explained by coherent contributions from direct interaction and compound-nucleus formation. A spectroscopic factor was extracted for the DWBA calculation from the absolute cross-section measurements and found to be . Resonances in the compound-nucleus formation were found at 3.00 and 3.33 MeV (c.m.) with widths of 0.28 and 0.21 MeV and spins of , respectively. 相似文献
19.
The yield of γ-rays from the reaction 46Ti(p, γ)47V has been measured as a function of bombarding energy over the range 0.72–3.00 MeV, from 47Ti(p, γ)48V over the range 0.74–3.50 MeV, and from 48Ti(p, γ)49V over the range 0.72–4.40 MeV. The yields of γ-rays following (p, p') reactions on all three targets were also measured and (p, p') cross sections were deduced for the first excited state proton groups for 46Ti and 48Ti and for the first ten proton groups for 47Ti. The yield of neutrons from the reaction 47Ti(p, n)47V has been measured over the range from threshold to 4.40 MeV. All these data are compared with statistical-model calculations, and good agreement is achieved. Thermonuclear reaction rates for the (p, γ) and (p, n) reactions are calculated for the temperature range 5 × 108–1010 K which includes the range of temperatures of interest in nucleosysnthesis calculations. 相似文献
20.
D.V. Aleksandrov Yu.A. Glukhov A.S. Demyanova A.A. Ogloblln S.B. Sakuta V.V. Sukharevsky S.V. Tolokonnikov S.A. Fayans F.A. Gareev S.N. Ershov I.N. Borzov J. Bang 《Nuclear Physics A》1985,436(2):338-364
The reaction 14C(6Li, 6He)14N was investigated with 93 MeV 6Li ions in an angular interval of 7–26°. Angular distributions were analysed for the four most intense groups of 6He nuclei, corresponding to transitions to the ground (11+) and the excited (12+, 21?, 41?) states of 14N. In the theoretical analysis a mechanism of the spin-isospin excitation was suggested in the DWBA frame with the finite range of interaction and recoil in the light system (6Li6He) taken into account. In the calculations both shell-model wave functions and transition densities obtained in the theory of finite Fermi systems (FFS) were used. From the comparison between theory and experiment the Landau-Migdal force constant g′ is estimated in order to obtain some information on the degree of nuclear proximity to the threshold of pion condensation. 相似文献