共查询到20条相似文献,搜索用时 78 毫秒
1.
A. Kaplan H. Büyükuslu E. Tel A. Aydin M. H. B?lükdemir 《Indian Journal of Physics》2011,85(11):1615-1629
In this study, neutron-emission spectra produced by (n,xn) reactions up to 26 MeV for some deformed target nuclei as 165Ho, 181Ta, 184W, 232Th and 238U have been investigated. Also, the mean free path parameter’s effect for (n,xn) neutron-emission spectra has been examined.
In the calculations, pre-equilibrium neutron-emission spectra have been calculated by using new evaluated hybrid model and
geometry dependent hybrid model, full exciton model and cascade exciton model. The reaction equilibrium component has been
calculated by Weisskopf-Ewing model. The obtained results have been discussed and compared with the available experimental
data and found agreement with each other. 相似文献
2.
The discovery of neutron rich isotopes of the lightest elements on the neutron drip line exhibiting a halo structure has opened
up new vistas in research activities. The novel structural features associated with the halo phenomena have been the subject
for extensive theoretical and experimental investigations in recent times. In this talk, I propose to present a broad overview
of the recent developments in this field, bringing out the striking features which show that a large number oflight nuclei
near the neutron drip line are characterized by a clear separation between a ‘normal’ core nucleus and a loosely bound low
density veil of neutrons. Specifically, the two neutron halos offer a natural premises, from a theoretical standpoint, to
employ three body techniques for studying their detailed structural properties. A considerable part of the talk will be devoted
to report and highlight the results on a number of light halo nuclei such as 11Li, 11Be, 19B and 22C on which we have been carrying out investigations employing a simple but realistic three body model. These three body systems
which have been termed as ‘Borromean’ (i.e while three body systems are bound, the corresponding binary subsystems on the
other hand are unbound) are characterized by large spacial extension and very low separation energy of the neutron. They are,
therefore, ideally suited for exploring the possibility of the existence of Efimov states in two neutron halo nuclei. We have
recently carried out the three body analyses to predict the possibility of the occurrence of such states on which experimental
work at various laboratories is underway. 相似文献
3.
S. Vokál A. Vokálová A. Kravčáková S. Lehocká G. I. Orlova 《Physics of Atomic Nuclei》2008,71(8):1395-1402
The angular structures of particles produced in 208Pb-induced collisions with Ag(Br) nuclei in an emulsion detector at 158 A GeV/c have been investigated. Nonstatistical ringlike substructures in the azimuthal plane of the collision have been found and
their parameters have been determined. An indication of the formation of ringlike substructures from two symmetrical emission
cones, one in the forward and the other in the backward direction in the center-of-mass system, has been obtained. The ringlike
substructures’ parameters have been determined. The experimental results are in an agreement with I.M. Dremin’s idea that
the mechanism of the ringlike substructures’ formation in nuclear collisions is similar to that of Cherenkov electromagnetic
radiation.
The text was submitted by the authors in English. 相似文献
4.
It is shown that the analysis of fusion barrier distributions is not always an unambiguous test or a ‘fingerprint’ of the
structure information of the colliding nuclei. Examples are presented with same fusion barrier distributions for nuclei having
different structures. The fusion excitation functions for 16O+208Pb, using the coupled reaction channel (CRC) method and correct structure information, have been analysed. The barrier distributions
derived from these excitation functions including many of the significant channels are featureless, although these channels
have considerable effects on the fusion excitation function. However, a simultaneous analysis of the fusion, elastic and quasi-elastic
channels would fix the structure and the reaction unambiguously. 相似文献
5.
J. Adam K. Katovsky A. Balabekyan V. G. Kalinnikov M. I. Krivopustov H. Kumawat A. A. Solnyshkin V. I. Stegailov S. G. Stetsenko V. M. Tsoupko-Sitnikov W. Westmeier 《Pramana》2007,68(2):201-212
Target-blanket facility ‘Energy + Transmutation’ was irradiated by proton beam extracted from the Nuclotron Accelerator in
Laboratory of High Energies of Joint Institute for Nuclear Research in Dubna, Russia. Neutrons generated by the spallation
reactions of 0.7, 1.0, 1.5 and 2 GeV protons and lead target interact with subcritical uranium blanket. In the neutron field
outside the blanket, radioactive iodine, neptunium, plutonium and americium samples were irradiated and transmutation reaction
yields (residual nuclei production yields) have been determined using γ-spectroscopy. Neutron field's energy distribution
has also been studied using a set of threshold detectors. Results of transmutation studies of 129I, 237Np, 238Pu, 239Pu and 241Am are presented.
相似文献
6.
Fusion-evaporation cross-sections for the α-induced reactions upon197Au,193Ir,191Ir,185Re,181Ta,121Sb and69Ga nuclei at bombarding energies near the Coulomb barrier have been measured by off-line observation of the γ-rays emitted
in the radioactive decay of the residual nuclei using stacked foil technique. The total fusion cross-section for the systems
have been compared with simple statistical model calculations using the code ALICE/91 as well as with the coupled channel
calculations that include the β2 and ν4 slatic deformations and dynamic couplings of the vibrational/rotational states of the target and the projet tile using the
code CCDEF. 相似文献
7.
8.
New experimental data on fluctuations in the multiplicities of negatively charged particles in interactions of light nuclei
(p, d, 4He, 12C) with carbon nuclei at a momentum of 4.2 A GeV/c in 4π geometry are reported. The data indicate a behavior similar to that earlier observed by the NA49 Collaboration. The
cascade evaporation model, FRITIOF model, and UrQMD 1.3 model are used to analyze the data. The dependence of the fluctuations
on nuclear collision centrality is theoretically described without any exotic assumptions. According to the FRITIOF model,
the dependence of the multiplicity fluctuations on the collision centrality is to a large extent governed by fluctuations
in the number of “wounded” nucleons that are associated with the experimental observation conditions. The NA49 Collaboration
data are also described.
Original Russian Text ? A.S. Galoyan, E.N. Kladnitskaya, V.V. Uzhinsky, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ
i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 10, pp. 718–721. 相似文献
9.
JM Chatterjee M Saha Sarkar S Bhattacharya P Banerjee S Sarkar RP Singh S Murulithar RK Bhowmik 《Pramana》2001,57(1):165-169
High-spin states of 95,97Mo (Z=42, N=53,55) nuclei have been investigated through 82Se(18O, xn) reaction at Eb=60 MeV. The level scheme in 95Mo has been observed upto ≏ 10 MeV in the present experiment. The level structure shows mainly single particle character.
In 97Mo, the ground state level sequence has been extended to ≏ 4.5 MeV while the previous information had been up to 2.4 MeV.
A negative parity band built on 1437 keV (11/2−) excited state has been extended to 5.5 MeV. The structure seems to show a coexistence of single particle and collective
modes of excitation. Properties of both the nuclei have been compared with shell model calculations using OXBASH. 相似文献
10.
The generalized hybrid derivative coupling model has been applied to explore various ground state properties of different
nuclei. In this work we have confined our calculation only to the model characterized by the hybridization parameter α = 1/4
which gives better results than the other models of the same class, as we have seen earlier, for nuclear matter calculations.
The binding energy, single-particle energy spectra, density and charge radii of different doubly closed nuclei like 16O, 40Ca, 48Ca, 90Zr, 132Sn, 208Pb have been studied. The success of this model, in describing the doubly closed nuclei, motivates us to extend this calculation
further in the case of open shell nuclei after incorporating the pairing interaction and using a BCS transformation. We have
calculated the binding energy for such nuclei. We have also studied the isotopic shift for different Pb isotopes with respect
to 208Pb. We have compared our results with the other standard theoretical results as well as with the experimental values.
Received: 18 August 2000 / Accepted: 13 April 2001 相似文献
11.
Zh. I. Adymov N. Burtebayev S. B. Sakuta 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(7):914-916
Doppler shift attenuation was used to measure the lifetimes of 48Ti, 52Cr and 80Se nuclei excited states populated in the (n, n′γ) reaction using the neutron beam of the Republic of Kazakhstan’s WWR-K research
reactor. The measured data are in good agreement with the latest literature data. 相似文献
12.
A method of obtaining high polarization and pure spin states of impurity nuclei with a moderately strong quadrupole interaction
in solid diamagnetic hosts whose nuclei have spin 1/2, a large g factor (like 1H and 19F), and a high degree of polarization is proposed. The method employs cross-relaxation transitions of the impurity nuclei
with the host spins (with adiabatic variation of the external magnetic field) and simple radio-frequency pulses that invert
the host nuclei or give rise to two-spin resonance of the host and impurity nuclei.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 7, 539–543 (10 October 1998) 相似文献
13.
We discuss the non-radiative μ
− capture (i.e. ordinary muon capture, OMC) in light nuclei in terms of the nuclear shell model, and in the medium-and heavy-mass
nuclei in terms of the quasiparticle random-phase approximation. A new probe of the double-beta-decay matrix elements, namely
the use of the OMC to states of the intermediate nucleus of the double beta decay, is also addressed.
Presented by J. Suhonen at the Workshop on calculation of double-beta-decay matrix elements (MEDEX’05), Corfu, Greece, September
26–29, 2005. 相似文献
14.
Chengying Xie Xiaohong Zhou Yuhu Zhang Yingxiang Guo Xiangguo Lei Yong Zheng Minliang Liu Litao Song Hualei Wang Haiping Yu Wentao Guo Peng Luo Zhijun Wu Lihua Zhu Xiaoguang Wu 《中国科学G辑(英文版)》2005,48(4):442-449
High-spin states in 190Tl have been studied via the 160Gd(35Cl, 5nγ) reaction. The level scheme, consisting of the πh
9/2⊗vi
13/2 oblate band and a cascade with character of single particle excitations, has been established. Spin values have been firmly
assigned to the oblate band in 190Tl, resulting in low-spin signature inversion in the πh
9/2⊗vi
13/2 oblate band for the first time. Based on the similarity of the level structure in doubly odd Tl nuclei, spin values for the
oblate bands in 192–200Tl should be re-assigned, and a consistent low-spin signature inversion has occurred in these oblate deformed nuclei. The
low-spin signature inversion phenomena can be interpreted qualitatively by using the 2-quasiparticle plus rotor model including
p-n residual interactions. 相似文献
15.
M. Hunyadi A. M. van den Berg B. Davids M. N. Harakeh M. A. de Huu H. J. Wörtche M. Csatlós J. Gulyás A. Krasznahorkay D. Sohler U. Garg M. Fujiwara N. Blasi 《Physics of Atomic Nuclei》2007,70(8):1407-1414
The direct and statistical neutron decay of the isoscalar giant dipole resonance has been studied in 90Zr, 116Sn, and 208Pb using the (α, α’ n) reaction at a bombarding energy of 200 MeV. The spectra of fast decay neutrons populating valence hole states of the Z, N − 1 nuclei were analyzed, and estimates for the branching ratios were determined. The observation of the nucleon-direct-decay
channels helped to select giant-resonance strengths and suppress the underlying background and continuum, which led to an
indication of the existence of a new mode with L = 2 character, presumably the overtone of the isoscalar giant quadrupole resonance.
The text was submitted by the authors in English. 相似文献
16.
Data for coherent photoproduction of π0 mesons from nuclei ( 12C, 40Ca, 93Nb, natPb), recently measured with the TAPS detector at the Mainz MAMI accelerator, have been analyzed in view of the mass form factors
of the nuclei. The form factors have been extracted in plane-wave approximation of the A(γ,π0)A reaction and corrected for final-state interaction effects with the help of distorted-wave impulse approximations. Nuclear
mass rms radii have been calculated from the slope of the form factors for q2 → 0. Furthermore, the Helm model (hard-sphere form factor folded with Gaussian) was used to extract diffraction radii from
the zeroes of the form factor and skin thicknesses from the position and height of its first maximum. The diffraction radii
from the Helm model agree with the corresponding charge radii obtained from electron scattering experiments within their uncertainties
of a few per cent. The rms radii from the slope of the form factors are systematically lower by up to 5% for PWIA and up to
10% for DWIA. Also the skin thicknesses extracted from the Helm model are systematically smaller than their charge counterparts. 相似文献
17.
R. I. Dzhioev B. P. Zakharchenya V. L. Korenev P. E. Pak M. N. Tkachuk D. A. Vinokurov I. S. Tarasov 《JETP Letters》1998,68(9):745-749
Dynamic polarization of 31P nuclei is observed in a self-organized system of InP islands grown by metalorganic-hydride epitaxy in an InGaP matrix. The
polarized nuclei produce an effective magnetic field which acts on the polarization of the excitonic radiation. Optical detection
of the magnetic resonance signal from 31P nuclei in the crystal lattice of nanosize InP islands is successfully carried out.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 9, 711–714 (10 November 1998) 相似文献
18.
O. Sorlin C. Donzaud F. Nowacki J.C. Angélique F. Azaiez C. Bourgeois V. Chiste Z. Dlouhy S. Grévy D. Guillemaud-Mueller F. Ibrahim K.-L Kratz M. Lewitowicz S.M. Lukyanov J. Mrasek Yu.-E. Penionzhkevich F. de Oliveira Santos B. Pfeiffer F. Pougheon A. Poves M.G. Saint-Laurent M. Stanoiu 《The European Physical Journal A - Hadrons and Nuclei》2003,16(1):55-61
The neutron-rich nuclei 23
60-63V have been produced at GANIL via interactions of a 61.8A·MeV 76Ge beam with a 58Ni target. Beta-decay to 24
60-63Cr has been investigated using combined β- and γ-ray spectroscopy. Half-lives of the 60-63V nuclei have been determined, and the existence of a beta-decay isomer in the 60V nucleus is strongly supported. The observation of low-energy 2+ states in 60Cr (646keV) and 62Cr (446keV) suggests that these isotopes are strongly deformed with β2 ∼ 0.3. This is confirmed by shell model calculations which show the dominant influence of the intruder g and d orbitals to obtain low 2+ energies in the neutron-rich Cr isotopes.
Received: 13 June 2002 / Accepted: 27 August 2002 / Published online: 17 January 2003
RID="a"
ID="a"e-mail: sorlin@ipno.in2p3.fr
Communicated by D. Guerreau 相似文献
19.
D.Q. Fang W.Q. Shen J. Feng X.Z. Cai H.Y. Zhang Y.G. Ma C. Zhong Z.Y. Zhu W.Z. Jiang W.L. Zhan Z.Y. Guo G.Q. Xiao J.S. Wang J.Q. Wang J.X. Li M. Wang J.F. Wang Z.J. Ning Q.J. Wang Z.Q. Chen 《The European Physical Journal A - Hadrons and Nuclei》2001,12(3):335-339
Measurements of reaction cross-sections ( σR's) for some proton-rich nuclei ( N = 11–15 isotones) on carbon target at intermediate energies have been performed on RIBLL of HIRFL. A larger enhancement of
the σR for 27P has been observed than for its neighboring nuclei. A large difference between the proton and neutron density distributions
(proton halo) is necessary to explain the enhanced cross-section for 27P within the framework of the Glauber model. Density distributions with HO-type core plus Yukawa-square tail and rms radii
for 27P have been deduced from the measured σR data for the first time, which conform the long tail in its densities as predicted by RMF calculations.
Received: 23 May 2001 / Accepted: 7 November 2001 相似文献
20.
A Szanto de Toledo N Carlin N Added E M Szanto M G Munhoz J Takahashi A Suaide M M de Moura 《Pramana》1999,53(3):483-483
Considerable interest has been devoted to fusion reactions between light heavy ions specially between weakly bound ones, due
to the anomalous decrease of the fusion cross sections when compared to the total reaction cross section in the energy region
around the barrier [1–4].
While the exact nature of the process responsible for the fusion cross section limitation at barrier energies is still unclear,
this study shows an inhibition of the yield as the system mass decreases, resulting from the progressive increase of the barrier
height and decrease of the effective barrier radius [3]. Furthermore, extensive efforts have been made recently in the study
of energy-damped binary yields from light heavy-ion collisions [2,4]. Based on the substantial amount of data accumulated
so far, it is now generally accepted and supported by the transition state model [4], that the observed yields arise mostly
from a fusion-fission process. Data on complete fusion, fusion-fission and ‘elastic fission’ for the 9Be, 10,11B+10,11B; 16,17,18O + 10,11B; 19F+12C; 6,7Li+9Be, 12C reactions among others, are presented. For the loosely bound nuclei it was found that the severe fusion cross section limitation
is due to a low survival probability of the weakly bound nuclei until the instant of the collision [1]. 相似文献