共查询到20条相似文献,搜索用时 28 毫秒
1.
Using a silicon filtered fission neutron beam of an energy width of 20 keV around 143 keV we measured the total cross sections for 37 nuclides and elements having mass numbers between 87 and 140 and determined thep-wave strength functions. The 3P-resonance atA=98 shows no splitting into theP 3/2?P 1/2 doublet. The narrow resonance peak and the following broad distribution of thep-strength function (A=103 to 140) can approximately be reproduced by deformed optical model calculations. The spin-orbit term in the optical potential is consistent with the spin orbit force in the shell model. For nuclei around the closed (N=50) neutron shell a shell effect in thep-wave strength function is indicated. 相似文献
2.
L. L. Litvinsky 《Zeitschrift für Physik A Hadrons and Nuclei》1994,349(2):147-153
A combined analysis of the available data on the primaryγ-ray intensities from the113Cd(n, γ) reaction atE n=1.9 and 24.3 keV neutron energies together with the data on113Cd neutron capture cross sections in theE n=3–200 keV energy region was carried out. The neutron strength functions were determined asS n0=(0.260±0.073) 10?4 and Sn1=(5.06±0.67) 10?4. No spin-orbit splitting of thep-wave neutron strength function was found. The energy dependence of theE 1 radiative strength function {ie147-01} was fitted by the Kadmenski-Furman model somewhat better than by a standard Lorentzian. TheM 1 giant resonance parameters were obtained as E G M 1 =8.8±1.6 MeV and Γ G M 1 = 4.7±2.6 MeV. The neutron capture cross section of113Cd from its isomeric state ({ie147-02}=11/2?, E 1 m =263.7 keV) was calculated. 相似文献
3.
M. Kicinska-Habior M. Dabrowska P. Decowski T. Matulewicz B. Sikora J. Toke J. Cseh E. Somorjai 《Zeitschrift für Physik A Hadrons and Nuclei》1984,318(3):329-331
Differential cross sections for nonresonant radiative capture of low energy protons (E p = 1,348 keV and 1,370 keV) by23Na nuclei exhibit features pointing to the virtual excitation of the giant dipole resonance (GDR) mode. Theoretical analysis carried out within the framework of the direct — semidirect capture model reveals an enhanced coupling of the GDR with the incident protonf-wave consistent with the microscopic structure of the GDR in thes-d shell nuclei. 相似文献
4.
A. Lindholm L. Nilsson I. Bergqvist R. Zorro N. Olsson B. Castel A. Likar 《Zeitschrift für Physik A Hadrons and Nuclei》1984,317(2):149-154
Using the28Si(n, γ)29Si reaction, transitions to the ground state and first excited state in29Si have been studied in the neutron energy range 3–14 MeV with improved neutron energy resolution (of about 100 keV). The 90° cross sections show considerable structure in the entire neutron energy range. Comparison with theoretical calculations shows that compound-nucleus and direct-semidirect processes account for the non-resonant part (smoothly varying part) of the cross section. A microscopic model is, however, required to describe the resonance structure. Continuum shell-model calculations have proven to be a very promising means towards a better understanding of the capture process in, and below, the giant resonance region in light nuclei. The angular distributions of gamma rays in the neutron energy range 8–14 MeV indicate that the capture reaction is mainly of direct character and that the effect of interference between the electric dipole and isoscalar quadrupole resonance is weak. 相似文献
5.
P-wave neutron strength functions of 21 nuclei, in the rare-earth and deformed region 138 <A < 202, have been extracted from the average capture cross sections measured using SbBe photoneutrons and activation technique. S-wave neutron contribution is computed using the s-wave resonance parameters available in literature and subtracted out from the measured total capture cross section to yield the p-wave neutron capture contribution from which the p-wave neutron strength functions are extracted. Present results are found to be in general agreement with the values reported in literature. The experimental p-wave neutron strength functions are also compared with the theoretical predictions based on the different versions of the optical model potential, and qualitative agreement is observed with the deformed optical model theory of Buck and Perey. Strong evidence for shell structure effects is also noticed. 相似文献
6.
A. S. Fomichev I. David Z. Dlouhy S. M. Lukyanov Yu. Ts. Oganessian Yu. E. Penionzkevich V. P. Perelygin N. K. Skobelev O. B. Tarasov R. Wolski 《Zeitschrift für Physik A Hadrons and Nuclei》1995,351(2):129-130
Secondary beams of4He and6He were produced through the transfer reactions with the 18.5 MeV/u11B and 35.5 MeV/u7Li primary beams. The fusion-fission cross sections have been measured for the4,6He +209Bi reactions at energies Ecm>1.5*Bfus. In the present experiment it was found that the fission excitation function for the neutron rich nuclei6He is significantly higher than for the4He nuclei. 相似文献
7.
J. Kvítek V. Hnatowicz J. Červená J. Vacík V. M. Gledenov 《Zeitschrift für Physik A Hadrons and Nuclei》1981,299(2):187-188
The nuclear reactions induced by thermal and 2 keV neutrons on22Na radioactive nucleus were studied. For the thermal neutrons a more accurate value of22Na (n,p)22Ne reaction cross section was obtained. A weak proton transition to the22Ne ground state was observed. The upper limits of cross sections for thermal neutron induced (n,∞) reaction and (n, p) reaction with 2 keV neut·rons are given. 相似文献
8.
The differential elastic neutron scattering cross sections of141Pr were measured at the incident neutron energies of 1.2, 1.7 and 1.9 MeV in the angular range between 25 and 150 degrees. At 1.7 MeV the differential inelastic neutron scattering cross sections corresponding toQ=?1122 keV, and at 1.9 MeV the ones corresponding toQ=?1122, andQ=?1295 keV were also determined. In a transmission experiment, the total cross section was measured between 0.50 and 2.42 MeV. The total and differential cross sections were calculated using the nuclear optical model. The calculated results were compared with the experimental data. 相似文献
9.
10.
M. Eckhardt D. Hasselkamp K. -H. Schartner 《Zeitschrift für Physik A Hadrons and Nuclei》1979,292(4):337-345
The excitation of all ten levels of the neon 2p 53p configuration by proton impact (100 keV-1 MeV) has been investigated by the spectral analysis of photon emission. Absolute emission cross sections have been obtained by calibration with a standard light source. Cascade effects are shown to be very important especially in the case ofJ=1 levels. For the 3p(1 S 0) level, which we studied additionally for electron impact excitation (100 eV-1 keV), our experimental cross sections are compared with the first Born approximation. Furthermore the polarization of sixteen 3p—3s emission lines has been measured as a function of impact energy. The energy dependence of the line polarization is characterized by theJ quantum numbers of the atomic states involved in the respective transition. An anomalous polarization of all lines originating from the decay ofJ=1 levels has been found and is referred to dominant cascade effects. 相似文献
11.
The (p, t) reaction on the even isotopes of samarium has been investigated at a proton energy of 25.5 MeV. Angular distributions were obtained in the range 18° ≦ θ ≦ 148° with angular steps between 2° and 5°. The experimental energy resolution varied between 35 keV and 50 keV FWHM. Spin and parity assignments are performed by comparing the measured angular distributions to zero-range DWBA calculations. Some difficulties of DWBA calculations for (p, t) reactions are pointed out. The relative cross sections for transitions to different levels of the final nuclei are compared with other (p, t) and (t, p) measurements in the same region of the rare earth isotopes. The dependence of the (p, t) cross sections for different transitions on the neutron number of the final nuclei is discussed. Some 2+ states observed in (p, t) and (t, p) reactions are described in the quadrupole pairing vibrational picture. 相似文献
12.
W. R. McMurray K. Bharuth-Ram S. M. Perez 《Zeitschrift für Physik A Hadrons and Nuclei》1984,315(2):189-195
Proton spectra have been measured at lab angles ofθ=0° to 100° for the reaction Zr(n, p)Y at 21.8 MeV incident neutron energy. Spectra over an angular spread of 80° were accumulated simultaneously using a detection system consisting of proportional counterΔE detectors and a curved plastic scintillator as energy detector. Resonant behaviour is observed in the proton spectra for the Zr(n, p)Y reaction but not for the Fe(n, p)Mn reaction. The resonant structure is attributed to the excitation of the analogues ofT > giant dipole states of Zr. The resonant structure is shown to correspond in position, gross and fine structure, and, in strength and angular dependence of the cross sections, with expectations for the90Zr(n, p)90Y reaction. DWBA cross sections are derived and fitted to the experimental data with a Lane potential of 150 MeV. 相似文献
13.
L. Koester K. Knopf W. Waschkowski A. Klüver 《Zeitschrift für Physik A Hadrons and Nuclei》1984,318(3):347-356
Coherent neutron scattering lengths and total cross sections were measured on elemental Ga, Ga-compounds and on isotopically enriched samples at neutron energies from 0.5 meV up to 143 keV using different techniques. From the experimental data the following quantities could be obtained: the coherent scattering length of Ga and the spin state scattering lengths of the isotopes. the potential scattering radii (R′) the absorption cross sections of Ga,69Ga,71Ga and75As. As derived quantities are given the coherent and incoherent cross sections and the resonance spin scattering lengths for theJ=1 andJ=2 states of70Ga and72Ga. The physical meaning of these data and ofR′ and the comparison with the resonance parameters are considered. 相似文献
14.
A multilevel R-matrix analysis of Si neutron cross-section data measured at NBS has been performed up to about 4.5 MeV neutron energy. Only a small fraction of the p- and s-wave s.p. strength is observed, but both exhibit local concentrations of strength indicative of doorway structure around 1 and 0.2 MeV, respectively. Besides the well-known 180 keV, strong, resonance, the s-wave resonance structure is of moderate strength and widely distributed. The f- and d-wave assignments are not unambiguous, but J > 3/2 resonances show strong signs of intermediate structure for d-waves. A possible correlation between neutron and gamma decay channels and the connection between the states observed in (n, n), (d, p), (n, γ), and (γ, n) channels is discussed. A coreparticle doorway interpretation for s and p- waves is presented. 相似文献
15.
We study the inclusive (y,¯ p) and (p,p) reactions in nuclei and check the sensitivity to the¯p annihilation mechanisms. We find that including the many body annihilation mechanisms in nuclei reduces appreciably the cross section of these reactions with respect to the evaluation considering only the one body mechanism of¯p annihilation. This shows that the¯p production reactions are more sensitive to¯p annihilation than the direct¯p annihilation reactions and makes the production experiments very useful tools to investigate the complex mechanisms of¯p annihilation in nuclei. 相似文献
16.
Theoretical values ofs-,p- andd-wave proton strength functions were calculated for the target mass region between 30 to 70 and for the incident proton energy region of 2–4.75 MeV. They were compared with experimental results. Good agreement was observed for thes- andp-wave proton strength functions. 相似文献
17.
Neutrons of energies within a 50 eV interval at 1970 eV have been selected from reactor neutrons by means of resonance scattering on a target of63Cu and subsequently by the 1970 eV resonance of a80Se target. Insertion of stationary filters and the technique of difference measurements with a resonance filter resulted in a high selectivity, which allowed the determination of cross sections for quasi-monoenergetic neutrons for the elements: H, C, O, F, Na, Mg, Al, Si, P, Cl, K, Ca, Sc, Ti, V, Mn, Co, Ni, Cu, Ga, Pb and Bi. The precision cross sections of Pb and H contribute to investigations of fundamental neutron interactions. The measured σ(Pb)=11.198±0.003 b was recently used to deriveα n=(0.8±1)10?3 fm3 for the electric polarizability of the neutron. The neutron-proton cross sectionσ(1 H)=20.13±0.03 b and data at 143 keV, 〈1.3〉 MeV, 〈2.1〉 MeV and from the literature provide a refined set of the scattering parameters for the shape-independent effective-range approximation of the neutron-proton interaction. 相似文献
18.
R. A. Emigh C. A. Fields M. L. Gartner L. E. Samuelson P. A. Smith 《Zeitschrift für Physik A Hadrons and Nuclei》1982,308(2):165-171
Levels of120,122Sb have been observed using the121,123Sb(p, d) reactions atE p = 26.2 MeV. Thirty-two levels of120Sb and thirty-four levels of122Sb are observed below 2.0 MeV excitation with an energy resolution better than 25 keV FWHM. Experimental angular distributions were compared to DWBA calculations in order to extractl-transfers and spectroscopic factors. Strong mixing between the 3s 1/2, 2d 3/2, 2d 5/2, and 1g 7/2 neutron orbitals is observed in both nuclei. Nuclear Reactions:121,123Sb(p, d),E=26.2 MeV; measuredσ(E d ,θ).120,122Sb deduced levels,l,J,π, spectroscopic factors. Enriched targets, magnetic spectrometer. 相似文献
19.
J.G Malan W.F.E Pineo M Divadeenam B.H Choi E.G Bilpuch H.W Newson 《Annals of Physics》1975,89(2):284-298
Neutron total cross section measurements of natural Sr were made from 50–875 keV using a high resolution proton beam and the 7Li(p, n) reaction as a neutron source. These data were analyzed with the help of an R-Matrix code to extract resonance (energies and other) parameters up to about 850 keV. 2p-1h and particle-vibration doorway interpretation of the s-, p- and d-wave resonances is attempted in terms of the sum rule Σγn2 = γd2. Predictions based on both of these models agree with the experimental results. As expected the p-wave resonances are stronger than either s- and d-wave structure. Theory accounts for the p-wave strength remarkably well. Possible location of the p-wave s.p. resonance is reproduced with a real potential and its damping due to the imaginary potential is calculated.More fragmentation of the strong p-wave doorways is observed than was expected for a compound nucleus so near 90Zr, but a larger strength function is observed apparently due to the p-wave giant resonance. 相似文献
20.
Th. Kern P. Betz E. Bitterwolf F. Glatz H. Röpke 《Zeitschrift für Physik A Hadrons and Nuclei》1980,294(1):51-64
Theγ-decay modes of38Ar levels withE x ≦11,630keV and of42Ca levels withE x ≦10,036keV have been studied using the35Cl(α, pγ) reaction at 16MeV and the39K(α, pγ) reaction at 15.14 MeV, respectively. In both nuclei the number of states withJ≧6 exceeds fifty. Weak coupling calculations of the Bansal and French type reproduce the density of high-spin states. The success of the model implies that the excitations of up to four particles from thed 3/2 into thef 7/2 shell play a role in both nuclei. The structure of deformed states was found to be predominantly 4p/s 6h in38Ar and 4p/s 2h in42Ca, respectively. 相似文献