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1.
As an application of the inverse scattering technique of Marchenko, the single channelnp potentials1 P 1,3 P 1,3 D 2,3 P 0 and1 D 2 are generated. Phase shift analyses below 1 GeV of Virginia serve as input. In these analyses, the3P0 and the1D2 channels contain inelasticities above pion threshold. This work makes the first application of Marchenko's technique to higher partial waves and to nonunitary scattering functions.  相似文献   

2.
Radiative neutron capture in natural Cu has been studied in the neutron energy range from 200 eV to 16.5 keV. An area analysis of the data yields information on resonance parameters: For large resonances (Γ n ?Γ γ ) with known isotopic assignments values ofΓ γ or, if the spin of the resonance is unknown, 2g Γ γ are obtained. In some cases, it was possible to assign the spin of the resonance from the measured 2g Γ γ assuming a fairly constant radiation width. For a number of small resonances (Γn?Γ γ ) with unknown isotopic assignment, values of 4a n (a=isotopic abundance) have been determined. The distribution of these values, including those of the stronger resonances known from literature, shows an excess of small widths which is attributed top-wave levels. From this, thep-wave neutron strength function for natural Cu is estimated to be $$S_1 = \left( {0.30_{ - 0.14}^{ + 0.18} } \right)10^{ - 4} $$ .  相似文献   

3.
《Nuclear Physics A》1987,465(3):413-428
Neutron capture γ-rays have been observed from the low-lying resonances of 54Fe using the Harwell electron linear accelerator HELIOS as a neutron source. Relative values for the partial radiative widths of resolved lines were obtained by area analysis of the γ-rays peaks over neutron resonance regions, and absolute values were obtained by a shape analysis fit to the yield deduced by comparison with a 10B(n, αγ)7Li measurement. For the 7.8 keV s-wave resonance, a comparison of the partial widths with the predictions of the valence model has been made. In both relative and absolute senses, there is good agreement.  相似文献   

4.
A coupled-channel treatment of isospin-dependent optical potentials (ISOCCBA) has been developed to study two-nucleon transfer reactions. This formalism has been applied to the analysis of reactions populating isobaric multiplets in the region 40 ≦ A ≦ 56. A comparison is made of this calculation with the isospin-defined and charge-defined distorted-wave approximations.  相似文献   

5.
Importance of the velocity dependent terms upon the form of the energy dependence of the neutron asymmetry in muon capture by deuterons is demonstrated.  相似文献   

6.
7.
The energy distribution of neutrons following muon capture in heavy nuclei is investigated. It is shown that the experimental high energy tail (E > 10 MeV) of the neutron distribution can be explained by a direct emission process.  相似文献   

8.
Experimental differential cross sections for the optical collision process Na(3s)2S + Xe +  → Na(3p)2P + Xe are presented. By comparison with the results of accurate quantum calculations, the observed oscillatory structure is used to investigate the X2Σ and B2Σ potential curves of the NaXe van der Waals molecule. The repulsive branches of both curves are probed in addition to the binding minimum of the ground state. A value of 92 cm-1 is obtained for the dissociation energy.  相似文献   

9.
Nuclear dissipation in capture reactions is investigated using backtracing, a new analysis protocol. Combining analysis procedure with dynamical models, the difficult and long-standing problem of competition and mixing between quasifission and fusion-fission is solved for the first time. The nature of the relevant dissipation is determined as one-body dissipation. At low excitation energy where shell effects are strongly effective, the shape of the mass distribution could be a powerful check of the nature and the magnitude of the dissipation.  相似文献   

10.
The transition rates for muon capture in deuterium are calculated using the Reid soft-core deuteron, and 1S0 and 3PJ (J = 0, 1, 2) neutron-neutron wave functions. The validity of the closure approximation and of the Omnés-Muskhelishvili method is studied. The off-shell effects admissible in a class of phase-shift-equivalent potentials by present experimental data are evaluated.  相似文献   

11.
Fast neutron capture γ-ray spectra in 45Sc and 139La exhibit anomalous intensities for transitions to low-lying states with large neutron angular momenta. As statistical and valence models cannot adequately explain the observed spectra, a 2p-1h capture mechanism is proposed.  相似文献   

12.
《Nuclear Physics A》1988,480(1):20-28
We have analysed proton scattering cross sections and polarisations from 40Ca and 208Pb at intermediate energies using optical potentials calculated from Brueckner theory with internucleon potentials and ground state densities both different from those used previously. We show that the calculated results are very sensitive to the assumed densities and that agreement with experiment is only obtained using phenomenological densities and is not obtained using shell-model densities. We are not able to obtain agreement with the experimental data with a particular soft-core potential, Urbana V-14.  相似文献   

13.
A theory is presented to calculate potentials for the elastic nuclear heavy-ion scattering in a phenomenological way. The density properties of finite nuclei are derived with a schematic ansatz for the interaction energy between nuclear matter. The same interaction energy is applied to the calculation of the real part of the heavy-ion potential, which is of the quasimolecular type. The imaginary part is connected with the outflow time of nuclear matter out of compressed regions of overlapping nuclei. The resulting cross section for the elastic O16-O16 scattering reproduces the experiment up to 30 MeV quite well. An effective compression modulus of the S32 compound system can be deduced from the scattering experiment. It results to be about 200 MeV.  相似文献   

14.
We argue that the energy dependence of the meson-nucleus optical potential should be treated in a more dynamical fashion. When this is done, some of the difficulties found in phenomenological applications are eliminated.  相似文献   

15.
The Watson multiple scattering formalism for the optical potential describing elastic nucleon-nucleus scattering is developed while paying careful attention to the kinematics. No approximations are made in handling the recoil of the target nucleus so that internal and external energies can be uniquely separated. The resultant formalism allows a careful examination of the impulse, form-factor, and closure approximations without the confusion of the admixture of recoil energies; it also allows an explicit display of the nuclear correlations due to target recoil. With the many necessary (but incompletely understood) approximations explicity displayed, it appears that their confluence makes it unlikely that meaningful information about dynamical correlations in light nuclei can be obtained from elastic double-scattering experiments.  相似文献   

16.
We discuss the local and non-local pion-nucleus optical potentials. We find that the local potential becomes non-local when two-nucleon correlations are included. The two potentials (including correlations) can be made local through a transformation on the wave function. The new local potentials agree up to quadratic terms when expanded in powers of the density. The influence of finite-range correlations and off-shell pion-nucleon form factors is also investigated.  相似文献   

17.
18.
We have studied neutron transfer reactions induced by 132Xe on three rare-earth targets at EVC ~ 1.1. By using particle-particle-γ coincidence techniques we were able to identify final products and states populated in the one- and two-neutron reactions.The dependence of the transfer probabilities on the distance of closest approach is discussed in terms of effective penetration factors. The results seem to indicate the importance in two-neutron transfer of intermediate states with ? 6 MeV of excitation energy. The effect of excitation energy on the enhancement of the two-neutron transfer is discussed. A qualitative interpretation of the spin dependence of the one-neutron γ-ray yields in terms of the spatial localization of the wave functions involved is given.  相似文献   

19.
The level structure of Sr88has been investigated at the Karlsruhe research reactor FR2 using thermal neutron capture in Sr87. A pure thermal neutron beam was obtained by Bragg reflection from a lead single crystal. The target was natural strontium which gives a cross section contribution of about 87% for the reaction Sr87(n,γ) Sr88. High resolution measurements of the capture gamma ray spectrum have been performed by means of a 4 cm2 × 0.5 cm lithium-drifted germanium diode. 146 gamma lines have been observed. Cascade relationships were studied by a double and triple coincidence apparatus containing 4″Ø × 5″ NaI(Tl) crystals and XP-1040 photomultipliers. In several cases coincident background was subtracted utilizing the doublewindow technique. By application of the triple sum coincidence method capture gammas from isotopes other than the investigated Sr88 nucleus could be eliminated. Several new levels were established. A transition scheme is proposed and discussed. The neutron binding energy of Sr88 is determined to be 11111±4 keV.  相似文献   

20.
An approach which makes the first order pion-nucleus optical potential theoretically sound is presented. This study should permit higher order improvements to the potential to be more meaningful and the nuclear structure information extracted from pi-nucleus scattering to be more reliable. Based on multiple scattering theory, three optical potentials are constructed and studied in momentum space. These models are the popular Kisslinger potential, the local “Laplacian” potential, and an “improved off-shell potential;” the latter one is derived from absorptive separable pion-nucleon potentials which exactly reproduce on-shell πN scattering. By working in momentum space and explicitly including πN resonances and off-shell effects in the definition of the optical potential, the approach described here is capable of handling any number of pi-nucleon partial waves, is applicable over a very wide energy region, is based on a physical model for off-shell behavior, and is extended easily to include higher order effects. The optical potentials are inserted into two different relativistic wave equations to determine the total cross section and elastic differential cross section for pi-nucleus scattering. It is found that the various models for off-shell πN scattering determine significantly different πC12 scattering, with the improved off-shell model preferred on theoretical grounds. Also discussed is the importance of properly transforming πN scattering to the pi-nucleus c.m. system, the origin of the shift in the peak position of the π?C total cross section, and the reason for the increased diffractive nature of the differential cross section at 180 MeV.  相似文献   

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