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Based on a refined resonating group method a microscopic multi-channel calculation for the reactions 7Li(p, p)7Li and 7Li(p, n)7Be has been performed. Diagonal S-matrix elements and differential cross sections are presented from the 7Li-p threshold up to E = 2.5 MeV c.m. and compared with experimental data. 相似文献
3.
F. Hinterberger P.v. Rossen E. Lebsanft P. Lütticken J. Bisping R. Jahn B. Schüller 《Nuclear Physics A》1976,259(3):385-398
In a high resolution study of the 4He + α initiated excitation functions in the region of the 8Be first T = 2 state, weak resonance excursions have been observed in some reaction channels yielding the total width Γ = 14.7 ± 4.0 keV. No resonance excursion has been observed in the 4He + α elastic scattering yielding the branching ratio Γα/Γ ≦ 0.003 for the decay of the 8Be first T = 2 state into two α-particles. For the decay to the low-lying states of 6Li and 7Li lower limits of the branching ratio are given. The reinvestigation of the 7Li+p initiated excitation functions revealed no resonance anomaly in the region of the 8Be first T = 2 state. The upper limit Γp/Γ ≦ 0.023 has been derived for the proton decay to the 7Lig.s.. The results are compared with previous measurements and with shell-model calculations. 相似文献
4.
The charge-exchange reaction (7Li, 7Be is described in the frame of a microscopical DWBA with central effective forces. The transition density for 7Li-7Be is calculated in two ways: with a one-particle model and with a cluster model, taking full account of recoil effects. The formalism is used for the cases of (7Li, 7Be reactions with 6Li and 40Ca. Further cross sections for reactions on 12C and 16O with and excitation energies around 4.5 and 6.2 MeV, respectively, are compared to new data obtained at the Kurchatov Institute. Here particle-hole states in an oscillator model were used to characterize the heavy system. Angular distributions are well reproduced, but absolute cross sections are 6–7 times too small. This indicates that the assumption of a direct one-step process is correct, but that tensor forces should be included as a component of the effective nucleon-nucleon force. 相似文献
5.
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
6.
Z.E. Switkowski J.C.P. Heggie D.L. Kennedy D.G. Sargood F.C. Barker R.H. Spear 《Nuclear Physics A》1979,331(1):50-60
The cross section of the reaction 6Li(p, γ)7Be has been measured using Ge(Li) γ-ray spectrometers for proton bombarding energies Ep from 200 keV to 1200 keV. At Ep = 800 keV, the total (p, γ) integrated cross section is found to be 3.1 ± 0.4 μb. The cross section adopted from consideration of this and previous measurements is in good agreement with that predicted from the known thermal neutron cross section for 6Li(n, γ)7Li on the assumption that properties of mirror direct capture reactions can be well described by optical potentials that use the same parmeter values for the two reactions. 相似文献
7.
Angular distributions have been measured for the 54Fe(7Li, 6Li/6He)55Fe, 55Co reactions at . Exact finite-range DWBA calculations for both reactions, employing Woods-Saxon real and imaginary potentials to generate the distorted waves, reproduce the shape of the f-state angular distributions but not the rate of fall-off with increasing angle for p-states. Using real potentials constructed by double-folding a microscopic nucleon-nucleon potential with a Woods-Saxon shaped imaginary potential to generate the distorted waves did not change the calculations. The forward angle (7Li, 6He) data allowed the states in 55Co to be located and the determination of the single-particle centroid energies. The 55Co spectroscopic factors are in good agreement with those from the (d, n) reaction but are generally 25 % lower than those from average (3He, d) results. The 55Fe spectroscopic factors are in good agreement with (d, p) results. 相似文献
8.
J.L. Osborne C.A. Barnes R.W. Kavanagh R.M. Kremer G.J. Mathews J.L. Zyskind P.D. Parker A.J. Howard 《Nuclear Physics A》1984,419(1):115-132
Cross sections for the 3He(α, γ)7Be reaction have been measured at several energies from Ec.m. = 165 to 1169 keV by counting prompt γ-rays from a windowless, differentially pumped, recirculating, 3He gas target. The cross-section factor S34(Ec.m.) and branching ratio γ1/γ0 were determined at each energy. Cross sections were also measured at Ec.m. = 947 and 1255 keV by counting the γ-rays from the 7Be produced in a 3He gas cell with a Ni entrance foil. Combining the results of these two independent experiments yields a zero-energy intercept for the cross-section factor of S34(0) = 0.53 ± 0.03 keV · b. The relationship between these measurements and several theoretical calculations, and the import of the extrapolated cross section for the solar-neutrino problem are discussed. 相似文献
9.
Cross sections were determined for the 6Li(d, n)7Be reaction between 100 and 180 keV deuteron energy using the activation method. Different methods of extrapolation were employed and compared down to the energy region of astrophysical interest. 相似文献
10.
Angular distributions have been measured for transitions to low-lying states in 143Pm and 145Eu populated by the 142Nd(7Li, 6He)143 and the 144Sm(7Li, 6He)145Eu reactions at MeV. Elastic scattering of 7Li at 52 MeV on 142Nd and 144Sm, and 6Li at 46 MeV on 142Nd and at 45 MeV on 144Sm, were measured. Optical-model parameters extracted from fits to the scattering data were used in a finite-range DWBA analysis of the angular distributions for levels below 1.40 MeV excitation energy in 143Pm and 1.84 MeV in 145Eu. The reaction cross sections forward of 6° c.m. allow unambiguous distinction to be made between 2d and 2d final states. Final-state spins have been assigned to d-states in 143Pm at 1.40 MeV(+)and in 145Eu at 1.042 MeV (+). Existing assignments to other levels in both residual nuclei have been confirmed. 相似文献
11.
A.G. Teufel 《Nuclear Physics A》1974,235(1):19-26
Calculations for the two 5/2 ? resonances of the mirror nuclei 7Li and 7Be are performed within the framework of cluster representations of nuclei. Using the same microscopic forces for both nuclei, their phase-shift and resonance width differences in the energy region of the 5/2 ? resonances are shown to be mainly due to effects produced by the Coulomb interaction. 相似文献
12.
The charged-particle reaction channels accessible in the bombardment of 10B targets by 7Li nuclei of 24 MeV incident energy are investigated by measuring all ejectiles up to Be. Except for tritons, the reactions with light ejectiles proceed mainly via the formation of a compound nucleus, whereas some of the reactions with ejectiles heavier than the α-particle can be described by a direct mechanism. 相似文献
13.
The cross section for the radiative capture reaction 3He(4He, γ)7Be has been measured at 525 keV in the centre-of-mass by detection of prompt capture γ- rays. The targets were 3He-implanted Nb foils that allowed us to circumvent the experimental difficulties inherent in the use of extended gas cells for absolute measurements. The results give an inferred zero-energy cross-section factor of S34(0) = 0.47 ± 0.04 keV · b. The present result is compared with results from previous capture γ-ray yield and 7Be-activity methods of measuring the cross-section factor. 相似文献
14.
《Physics letters. [Part B]》1988,202(4):475-478
The nuclear-matter radii of 7Be and 7Li measured in high-energy heavy-ion reactions have been calculated and applied to the estimate of astrophysical S-factors for the 3He(α,γ)7Be and 3G(α,γ)7Li reactions. The absolute S(O) values in the KeV b are constrained to be 0.36<S(0)<0.63 and 0.083<S(0)<015 for the 3He(α,γ)7Be and 3H(α,γ)7Li reactions, respectively. 相似文献
15.
N. G. Peresadko Yu. A. Aleksandrov V. Bradnova S. Vokál S. G. Gerasimov V. A. Dronov P. I. Zarubin I. G. Zarubina A. D. Kovalenko V. G. Larionova A. I. Malakhov P. A. Rukoyatkin V. V. Rusakova S. P. Kharlamov V. N. Fetisov 《Physics of Atomic Nuclei》2007,70(7):1226-1229
At the JINR Nuclotron, 7Li nuclei are accelerated. The charge-exchange reaction involving these nuclei at an external target provides a secondary 1.23-A-GeV 7Be beam. This beam is used to irradiate emulsion chambers. The mean free path λinel(7Be) = 14.0 ± 0.8 cm for inelastic 7Be interactions in an emulsion coincides within the errors with those for 6Li and 7Li nuclei. More than 10% of the 7Be events are associated with the peripheral interactions in which the total charge of the relativistic fragments is equal to the charge of the 7Be nucleus and in which charged mesons are not produced. An unusual ratio of the helium isotopes is revealed in the composition of the doubly charged fragments of the 7Be nuclei: the number of the 3He fragments is twice as large as that of the 4He fragments. Each of 50% of peripheral interaction events includes two doubly charged fragments. The channels of the 7Be fragmentation into charged fragments are presented. In 50% of events, the 7Be fragmentation occurs only into charged fragments without the emission of neutrons. The 4He + 3He channel dominates, whereas each of the 4He + d + p and 6Li + p channels constitutes 10%. Two events without neutron emission are observed in the 3He + t + p and 3He + d + d three-body channels. The mean free path for the coherent dissociation of relativistic 7Be nuclei into 4He + 3He is equal to 7 ± 1 m. The main features of the fragmentation of relativistic 7Be nuclei in such peripheral interactions are explained by the 3He + 4He two-cluster structure of the 7Be nucleus. 相似文献
16.
J. Ero Z. Fodor P. Koncz Z. Seres M. Csatlós B.A. Khomenko N.N. Khovanskij Z.V. Krumstein Yu.P. Merekov V.I. Petrukhin 《Nuclear Physics A》1981,372(3):317-330
The reactions 7Li(p, pd)5He and 12C(p, pd)10 were investigated at 670 MeV in quasi-free scattering geometry at large angles. In transitions to low-lying as well as to highly excited states of the residual nuclei the energy distributions of the scattered protons are in agreement with the mechanism of quasi-free scattering on quasi-deuterons in the p- and s-shells of 7Li and 12C. 相似文献
17.
S. B. Sakuta B. G. Novatsky D. N. Stepanov D. V. Aleksandrov Yu. A. Glukhov E. Yu. Nikol'sky 《Physics of Atomic Nuclei》2002,65(10):1771-1777
The (6Li, 7Be) and (6Li, 7Li) reactions on 6Li and 7Li nuclei were investigated in the angular interval 0°–20° in the laboratory system at a 6Li energy of 93 MeV. In addition to low-lying states of the 5,6He and 5,6Li nuclei, broad structures were observed near the t(3He)+d and t(3He)+t thresholds at the excitation energies of 16.75 (3/2+) and ~20 MeV (for 5He), 16.66 (3/2+) and ~20 MeV (5Li), 14.0 and 25 MeV (6He), and ~20 MeV (6Li). The angular distributions measured in the 7Li(6Li, 7Be)6He reaction for transitions to the ground state (0+) and excited states at E x=1.8 MeV (2+) and 14.0 MeV of the 6He nucleus were analyzed by the finite-range distorted-wave method assuming the 1p-and 1s-proton pickup mechanism. The (6Li, 7Be) and (6Li, 7Li) reactions were shown to proceed predominantly through the one-step pickup mechanism, and the broad structures observed at high excitation energies are considered as quasimolecular states of the t(3He)+d and t(3He)+t types. 相似文献
18.
The (12C, 10Be) and (12C, 9Be) reactions on 58Ni were studied at 77 MeV. New levels were determined for both residual nuclei, 60Zn and 61Zn. For 61Zn, levels and a new ground state mass were also measured with the 64Zn(3He, 6He) reaction. A mass excess for 61Zn of ?56333±23 keV was obtained. Angular distributions for the 12C induced reactions are compared with finite range DWBA calculations and found to be insensitive to L? and J-transfer. 相似文献
19.
Measurements of the α-n angular correlation in the sequential reaction 7Li (d,α) 5He (g.s) → 4He + n indicate V that the 5He intermediate state does not break up symmetrically about the recoil centre-of-mass system. The angular correlation can be explained in terms of a compound nuclear reaction proceeding through levels in 9Be1. 相似文献
20.
The elastic scattering angular distributions for 7Li + 25Mg and 7Li + 27Al were measured at over angular ranges of 8–55° c.m. and 8–64° c.m. Previously published measurements for 24, 26Mg at 89 MeV and 24Mg at 34 MeV are reanalyzed. The cross sections were analysed using a 6-parameter phenomenological Saxon-Woods potential. No discrete ambiguities were found but the usual continuous ambiguities exist. The data were also analysed with double folded real potentials generated using the M3Y effective interaction. The folded potential must be multiplied by about 0.6 to fit the data. The extent to which 7Li optical-model potentials are determined and suggestions for further work on the normalization of the folded potential are discussed. 相似文献