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1.
The possibility to construct intercluster interaction potentials in continuous and discrete spectra is shown in one‐channel cluster model based on the classification of orbital states according to Young schemes. These potentials usually contain Pauli forbidden states, and correctly describe elastic scattering phase shifts taking into account resonance behavior and main characteristics of the bound states of nuclei in the considering cluster channel. The versions of intercluster interaction potentials describing the resonance nature of some phase shifts of the n7Li elastic scattering at low energies and the P2 ground state of 8Li in the n7Li cluster channel have been constructed for the demonstration of this approach. The possibility of describing the total cross sections of 7Li (n,γ)8Li within the energies from 5 meV (5 · 10‐3 eV) to 1 MeV, including resonance at 0.25 MeV, has been demonstrated for the potentials obtained in the potential cluster model with forbidden states. 相似文献
2.
A. V. Yatsenko 《Physics of the Solid State》1998,40(1):109-111
An experimental NMR study of the 6Li isotope in single crystals of lithium niobate has been performed, along with a computer simulation of 6Li NMR spectra for a crystal of congruent composition, containing defects in the cation sublattice. It is found that the mean
value of the principal component of the electric field gradient tensor at the 6Li nuclei is 1.48 times larger than at the 7Li nuclei. It is surmised that there is a substantial difference in the character of the mobility of the 6Li and 7Li nuclei in the LiO6 octahedra at room temperature.
Fiz. Tverd. Tela (St. Petersburg) 40, 122–125 (January 1998) 相似文献
3.
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
4.
《Nuclear Physics A》1986,457(1):173-181
Angular distributions for the transfer reactions 40Ca(7Li, 6Li)41Ca and 40Ca(7Li, 6He)41Sc have been measured at 34 MeV, in small angular increments out to angles where the cross section has fallen by four orders of magnitude. Finite range DWBA calculations show a high sensitivity to different distorting potentials at the largest angle cross sections. It is found that a combination of Woods-Saxon and double-folded potentials does the best job of reproducing the data over the whole angular range. 相似文献
5.
Local environments and dynamics of lithium ions in the binary lithium silicide Li13Si4 have been studied by 6Li MAS-NMR, 7Li spin-lattice relaxation time and site-resolved 7Li 2D exchange NMR measurements as a function of mixing time. Variable temperature experiments result in distinct differences in activation energies characterizing the transfer rates between the different lithium sites. Based on this information, a comprehensive picture of the preferred ionic transfer pathways in this silicide has been developed. With respect to local mobility, the results of the present study suggests the ordering Li6/Li7>Li5>Li1>Li4 >Li2/Li3. Mobility within the z=0.5 plane is distinctly higher than within the z=0 plane, and the ionic transfer between the planes is most facile via Li1/Li5 exchange. The lithium ionic mobility can be rationalized on the basis of the type of the coordinating silicide anions and the lithium-lithium distances within the structure. Lithium ions strongly interacting with the isolated Si4− anions have distinctly lower mobility than those the coordination of which is dominated by Si26− dumbbells. 相似文献
6.
B. M. Abramov Yu. A. Borodin S. A. Bulychjov I. A. Dukhovskoy A. P. Krutenkova V. V. Kulikov M. A. Martem’yanov M. A. Matsuk V. E. Tarasov E. N. Turdakina A. I. Khanov 《JETP Letters》2004,80(4):214-217
Quasielastic triton knockout from 6Li and 7Li nuclei by negative pions with momenta p 0=0.72 and 0.88 GeV/c was studied in the region of backward pion-triton scattering. The experiment was performed at the Institute of Theoretical and Experimental Physics (ITEP, Moscow) on a 3-m magnetic spectrometer equipped with spark chambers. The momentum distributions of the intranuclear quasitriton motion and the excitation-energy spectra of residual nuclei were obtained. 相似文献
7.
J. Cook 《Nuclear Physics A》1982,388(1):153-172
Simultaneous fits have been made to 44 6Li data sets covering the mass range 24–208 and the energy range 13–156 MeV in order to determine an average (“global”) optical-model potential for 6Li scattering. A similar study has been made for 25 7Li data sets over the same mass range and an energy range of 28–88 MeV to find an average 7Li potential. With Saxon-Woods form factors, constant values may be used for all parameters except for the depth of the imaginary potential which decreases in magnitude with increasing mass. The necessity of energy dependence. Coulomb correction and (for 7Li) a symmetry term is investigated. The variation of the integral properties of the potentials is discussed, and also a comparison is made for the two projectiles. Application of the global potentials is made to inelastic scattering and single-nucleon transfer reactions. 相似文献
8.
G. Gruber I. C. Dormehl K. Meier-Ewert K. Bethge 《Zeitschrift für Physik A Hadrons and Nuclei》1973,265(4):411-420
In a coincidence experiment, two excitation functions (0cm=60° and 90°) and four angular distributions of the differential cross section for the elastic scattering of6Li on6Li were measured. The energy range for the excitation functions was from 2 to 10 MeV (CM), the angular distributions were taken at CM-energies of 4, 5, 6, 7.25 MeV. Optical model calculations were performed. It is shown that the outer portion of the potentials is most important for reproducing the experimental data. 相似文献
9.
C. Signorini M. Mazzocco G.F. Prete F. Soramel L. Stroe A. Andrighetto I.J. Thompson A. Vitturi A. Brondi M. Cinausero D. Fabris E. Fioretto N. Gelli J.Y. Guo G. La Rana Z.H. Liu F. Lucarelli R. Moro G. Nebbia M. Trotta E. Vardaci G. Viesti 《The European Physical Journal A - Hadrons and Nuclei》2001,10(3):249-253
Large cross-section reaction channels were measured in the systems 6Li( 7Li) + 208Pb with high statistical accuracy at 5(3) energies around the Coulomb barrier from 29 to 39 MeV. These channels were assigned
(mainly) to the breakup of 6Li, very loosely bound, into α + d and to the breakup of 5Li, produced by n-transfer to the target, into α + p and to similar processes with 7Li beam. The cross-sections with 6Li, S
α = 1.475 MeV, are systematically larger than the 7Li ones. This reflects, most likely, the higher binding energy of 7Li, S
α = 2.468 MeV. Theoretical predictions for the 6Li + 208Pb system which include for 6Li breakup to continuum states within a continuum discretized coupled-channels approach (CDCC) and resonant breakup plus n-transfer
with DWBA reproduce the angular distribution shapes but still underestimate the cross-sections by a factor ∼ 3.
Received: 15 January 2001 / Accepted: 3 March 2001 相似文献
10.
Angular distributions and excitation functions for the emission of a large number of proton, deuteron, triton, and-particle groups in7Li+16O reactions have been measured in the vicinity of the Coulomb barrier. Within the framework of the statistical reaction model, two approaches are presented that can reproduce the only weakly anisotropic shape of the angular distributions and the absolute cross section for those groups of ejectiles where contributions from direct reaction modes are small. When a standard Woods-Saxon potential deduced from elastic scattering is used, the entrance channel angular momentum distribution must be limited to values below critical angular momental
cr which are smaller than the grazing angular momental
gr if fusion is to be described. A global proximity potential with a parameter set that has been adjusted to reproduce the fusion reactions of a variety of p- and sd-shell nuclei yields very similar results when applied to7Li+16O. The proximity potential effectively introduces a similar angular-momentum limitation. This analysis proves the existence of a fusion cross section limitation and the importance of strong direct reaction modes (transfer and possibly inelastic processes) in7Li+16O reactions at energies close to and even below the Coulomb barrier. Another aspect of7Li+16O is addressed briefly. The resonance-like structure observed in the heavy-ion radiative capture reaction7Li(16O,
0+1)23Na atE
x
(23Na)=25.4 MeV is not observed in the particle decay channels investigated in the present work.The authors would like to acknowledge the help received from B. Bellenberg, B. Dechant, H. Hemmert, T. Krischak, E. Kuhlmann, H. Putsch, and C. Scholz during the experiments. 相似文献
11.
W. Weiss P. Egelhof K.D. Hildenbrand D. Kassen M. Makowska-Rzeszutko D. Fick H. Ebinghaus E. Steffens A. Amakawa K.I. Kubo 《Physics letters. [Part B]》1976,61(3):237-241
Vector polarized 6Li nuclei have been elastically scattered on and on 16O, 28Si, 58Ni (E = 22.8 MeV). For the lighter nuclei surprisingly large asymmetries have been observed. The order of magnitude of the polarization effects observed can be understood within a folding model for the 6Li spin-orbit potential. 相似文献
12.
Angular distributions for the (7Li, 6Li) reaction on 28Si and 40Ca to ground and excited states of 29Si and 41Ca have been measured at . The shapes of the angular distributions are well described by exact finite-range DWBA calculations. To test the sensitivity of the calculated angular distributions to the exit channel potential, calculations were made using a strongly absorbing 7Li potential for both the entrance and exit channels. This calculation produced as good a fit to the shape of the angular distributions as did calculations with a 6Li potential in the exit channel, even though 7Li and 6Li elastic scattering on these target nuclei are not very similar. However, the magnitudes of the calculated cross sections are sensitive to the choice of potentials, and agreement with light-ion spectroscopic factors is obtained when the more weakly absorbing 6Li potentials are used. The spectroscopic factors obtained from the 40Ca(7Li, 6Li) reaction study are in good agreement with the extensive light-ion results showing that the absolute magnitude of the reaction is correctly predicted by exact finite-range DWBA calculations that use optical parameters determined from elastic-scattering data. 相似文献
13.
《Nuclear Physics A》1987,466(1):168-188
Elastic scattering cross sections for 10–170° c.m. have been measured for 7Li+11B and 7Li + 13C at 34 MeV. These data have been analyzed with the optical model using Woods-Saxon potentials, or potentials with a double-folded real part. The double-folded potentials were found to fit the data better, and quadrupole contributions were required to fit the large angle 7Li+11B data. In addition angular distributions for the (7Li, 8Li), (7Li, 6Li) and (7Li, 6He) reactions were measured. The transfer data were analyzed with finite-range DWBA calculations which were able to describe the shape of the data well and produced spectroscopic factors in agreement with theoretical and other experimental values. A phase shift of about 3° between the calculations and the data was found for the (7Li, 6Li) and (7Li, 6He) reactions. 相似文献
14.
S. B. Sakuta N. Burtebaev S. V. Artemov R. Yarmukhamedov 《Physics of Atomic Nuclei》2012,75(7):785-797
Existing experimental data on elastic and inelastic deuteron scattering on 6Li nuclei in the energy range from 8 to 50 MeV were analyzed within the approach of coupled reaction channels. The coupling of elastic scattering and inelastic scattering accompanied by the transition to the 3+ state at E x = 2.186 MeV and the mechanism involving the exchange of an alpha-particle cluster were taken into account in respective calculations. The phenomenological potentials obtained from the present analysis describe well experimental angular distributions at all energies and in full angular ranges. The depths of the real and imaginary parts of the potentials in question depend smoothly on energy at fixed values of the remaining parameters. The energy dependence of relevant volume integrals agrees well with similar data for the p + 6Li, ?? + 6Li, and 12C + 12C systems and with the predictions of a microscopic theory. 相似文献
15.
Yu. G. Abov A. D. Gulko F. S. Dzheparov O. N. Ermakov D. V. Lvov A. A. Lyubarev 《Physics of Atomic Nuclei》2014,77(6):682-694
Random walks in disorderedmedia are studied by considering the example of the delocalization of nuclear polarization in an ensemble of 8Li beta-active nuclei produced in (n, γ) reactions induced by polarized thermal neutrons in LiF single crystals. The process is initiated by magnetic dipole-dipole interactions. It consists in polarization transfer from a primarily polarized 8Li nucleus to the closest (stable) 6Li nuclei and in subsequent polarizationmigration over 6Li nuclei, the return of the polarization in question to the 8Li nucleus being possible. In order to obtain information about the polarization of 8Li nuclei, the asymmetry of beta radiation from them was measured with respect to the external magnetic field H 0. The process was studied until it reached the diffusion asymptotic regime. The concentration of 6Li was varied between 3% and 10%, while the field strength H 0 was changed from 200 to 1200 G. It is shown that microscopic theory is in satisfactory agreement with the experimental results obtained in the way outlined above. A comparison with the investigation of the mathematically allied process of the Förster electricdipole transfer of localized excitons is performed. 相似文献
16.
The problem of the origin of the quadrupole deformation in the 6Li ground state is investigated with allowance for the three-deuteron component of the 6Li wave function. Two long-standing puzzles related to the tensor interaction in the 6Li nucleus are known: that of an anomalous smallness of the 6Li quadrupole moment (being negative, it is smaller in magnitude than the 7Li quadrupole moment by a factor of 5) and that of an anomalous behavior of the tensor analyzing power T2q in the scattering of polarized 6Li nuclei on various targets. It is shown that a large (in magnitude) negative exchange contribution to the 6Li quadrupole moment from the three-deuteron configuration cancels almost completely the “direct” positive contribution due to the αd folding potential. As a result, the total quadrupole moment proves to be close to zero and highly sensitive to fine details of the tensor nucleon-nucleon interaction in the 4He nucleus and of its wave function. 相似文献
17.
Coupled-channels calculations for the elastic and inelastic scattering of K+ at 715 MeV/c by 6Li and 12C at 635, 715 and 800 kaon Lab momenta have been analysed. The optical potentials of 12C and 6Li are calculated in terms of the alpha-particle and deuteron optical potentials. Good fits to the experimental data and phenomenological
calculations are obtained for 6Li and 12C nuclei. 相似文献
18.
19.
20.
N. Burtebayev S. V. Artemov B. A. Duisebayev Zh. K. Kerimkulov S. B. Kuranov S. B. Sakuta 《Physics of Atomic Nuclei》2010,73(5):746-756
At an energy of 25 MeV and in the angular range 7°−175° in the laboratory frame, angular distributions were measured for elastic
deuteron scattering on 6Li nuclei and for the respective inelastic-scattering processes accompanied by the transitions to the ground state (1+) of
the 6Li nucleus and to its excited state at E
x
= 2.186 MeV (J
π = 3+). The resulting data were analyzed on the basis of the optical model of the nucleus and the coupled-reaction-channel method
with allowance for the mechanism of alpha-particle-cluster exchange. It is shown that only upon including, in the analysis,
channel coupling and the exchange mechanism can the experimental cross sections for elastic and inelastic scattering be reproduced
over the entire range of angles. 相似文献