共查询到20条相似文献,搜索用时 15 毫秒
1.
J. Görres H.W. Becker L. Buchmann C. Rolfs P. Schmalbrock H.P. Trautvetter A. Vlieks J.W. Hammer T.R. Donoghue 《Nuclear Physics A》1983,408(2):372-396
The direct capture process in the reactions 21Ne(p, γ)22Na and 22Ne(p, γ)23Na has been investigated at Ep = 0.3–1.6 MeV using neon gas enriched to 91 % in 21Ne and to 99 % in 22Ne, respectively. The gas was recirculated in a differentially pumped gas target system of the extended-static and quasi-point supersonic jet type. For 22Ne(p, γ)23Na, the direct capture process has been observed to several final states in 23Na up to Ex = 8.83 MeV excitation energy. The deduced spectroscopic factors C2S are in fair agreement with the corresponding values from stripping reactions. The capture transition into the 23Na ground state exhibits broad structures, which resemble Ericson fluctuations. The data remove the previously reported discrepancies in C2S for the 23Na ground state. The excitation functions for the 21Ne(p, γ)22Na reaction are dominated by broad and intense resonances, which hampered the measurement of the direct capture process. The nuclear and astrophysical aspects of the results are discussed. 相似文献
2.
The reactions 21Ne(p, γ)22Na and 22Ne(p, γ)23Na have been investigated at Ep(lab) = 70–355keV. Neon gas enriched to 91% in 21Ne and to 99% in 22Ne was recirculated in a differentially pumped gas target system of the extended-static and quasi-point supersonic jet type. For 21Ne(p, γ)22Na, new resonances were found at Ep = 126, 272, 291 and 352 keV. The 291 keV resonance corresponds to a new unbound state in 22Na. Excitation energies, γ-ray decay schemes, resonance widths and strengths as well as Jπ assignments are reported for all the resonances. Information on low-lying states in 22Na is also obtained. Of the 9 expected resonances in 22Ne(p, γ)23Na none has been observed. Upper limits on their ωγy strengths are presented. The astrophysical as well as the nulcear structure aspects of the results are discussed. 相似文献
3.
Angular distributions of the cross section and vector analyzing power have been measured for 8 levels in 21Ne using the 20Ne(, p)21Ne reaction. New spin assignments are made to the 4.52 MeV level () and the 5.69 MeV level (). Our results support a assignment to the 5.33 MeV level and disagree with the assignment to the 3.73 MeV level. 相似文献
4.
Angular distribution measurements have been performed on the 21Ne(p, d)20Ne and 21Ne(d, p)22Ne reactions at Ep = 20 MeV and Ed = 10.2 MeV, respectively. In the 21Ne(p, d) 20Ne reaction, the prolific formation of the Jπ = 2+, 1.63 MeV state was characterized by ln = 2 pickup, and the distribution associated with the 44, 4.25 MeV state was suggestive of a weak ln = 2 pickup. All of the observed ln = 1 pickup strength is associated with formation of the 2−, 4.97 MeV 20Ne level. The 21Ne(d, p)22Ne results indicate that ln = 2 transfer is involved in the formation of the 1.28, 3.36, 5.52, 5.63 and 6.65 MeV 22Ne states. The angular distribution observed for the 2+, 4.46 MeV state and also the unresolved 5.33, 5.36 MeV composite of states required both ln = 0 and ln = 2 components in the associated distorted-wave Born approximation fits. The spectroscopic factors extracted from the present results are compared with those predicted by the Nilsson model without mixing: Applications of the angular momentum projection rule to the 21Ne(d, p)22Ne reaction are considered. 相似文献
5.
D. K. Olsen A. R. Barnett S. F. Biagi N. H. Merrill W. R. Phillips 《Nuclear Physics A》1974,220(3):541-568
The static quadrupole moments of the first excited Jπ = 2+ states in 20Ne and 22Ne and the reduced electric quadrupole transition probabilities of these states to the ground states were measured via projectile Coulomb excitation. The quadrupole moments were deduced from the shapes of γ-ray angular distributions. The results are: Q(20Ne, 2+) = −0.20±0.05 b and Q(22Ne, 2+) = −0.11±0.05 b. The transition strengths were deduced from yield measurements and by comparison with the yields of target γ-rays. The results are: B(E2; 0+ → 2+, 20Ne) = 0.037±0.003 e2 · b2 and B(E2; 0+ → 2+, 22Ne) = 0.025±0.002 e2· b2. The results for the transition strengths are consistent with the results of accurate timing methods and resolve discrepancies between previous experiments. The results for the quadrupole moments are consistent with earlier measurements, although the mean values we obtain are slightly lower. The experimental measurements are compared with theoretical predictions and a detailed discussion is given of corrections to this type of reorientation experiment. 相似文献
6.
The 20Ne(p, γ)21Na capture reaction has been studied in the energy range Ep = 0.37–2.10 MeV. Direct-capture transitions to the states have been found with spectroscopic factors of C2S(1d) = 0.77±0.13 and C2S(2s) = 0.90±0.12, respectively. The high-energy tail of the 2425 keV state, bound by 7 keV against proton decay, has also been observed in the above energy range as a subthreshold resonance. The excitation function for this tail is consistent with a single-level Breit-Wigner shape for a γ-width of Γγ = 0.31±0.07 eV at Ex = 2425 keV. The extrapolation of these data to stellar energies gives an astrophysical S-factor of S(0) = 3500 keV · b. Two new resonances at Ep = 384±5 and 417± 5 keV have been observed with strengths of ωγ = 0.11±0.02 and 0.06±0.01 meV, corresponding to the known states at and 2829 keV (presumably ), respectively. For the known Ep = 1830 keV resonance, a strength of ωγ = 1.0± 0.3 eV and a total width of Γ = 180± 15 keV were found. Branching ratios as well as transition strengths have been obtained for these three states. The Q-value for the 20Ne(p, γ)21Na reaction (Q = 2432.3 ± 0.5 keV) as well as excitation energies for many low-lying states in 21Na have been measured. No evidence was found for the existence of the state reported at Ex = 4308±4 keV.In the case of 22Ne(p, γ)23Na, direct-capture transitions to six final bound states have been observed revealing sizeable spectroscopic factors for these states. The astrophysical S-factor extrapolated from these data to stellar energies, is S(0) = 67 ± 12 keV · b.The astrophysical as well as the nuclear structure aspects of the present results are discussed. 相似文献
7.
G.W. Bund 《Nuclear Physics A》1974,233(1):217-229
Stripping to analog resonances is studied by expressing the DWBA cross section in terms of the resolvent operator appropriate to the system composed of the proton and the target. The resolvent operator is decomposed, by means of the Feshbach projection operator technique, into parts corresponding to the entrance channel, the analog state and the compound states. The approximation scheme is similar to that used in our previous treatment of proton scattering at an analog resonance. The complex proton form factor depends on the Green function satisfying the inhomogeneous Schrödinger equation corresponding to elastic scattering and on the Coulomb potential generated by the target. The method is applied to (3He, d) stripping to analogs in 93, 95, 97Tc. 相似文献
8.
Extensive experimental data for the resonance scatttering of protons to the ground state and first excited state in 138Ba are presented. A Breit Wigner analysis with a background term of the form Σn(an/En) is performed and the extracted background function is compared with optical-model calculations using the parameters given in a detailed investigation by Perey. Neutron spectroscopic factors calculated in different ways from this data are compared with the corresponding factors from (d, p). An accurate determination of resonance energies for the first two resonances reveals a deviation from a constant Coulomb shift of the order of 10 keV. 相似文献
9.
We present predictions for nucleon-nucleon elastic scattering phase parameters based on a unitary, relativistic, one-pion-exchange model, which takes single-pion-production inelasticity into account. The agreement of the high-L phase shifts with data is considerably improved at intermediate energies by inclusion of the NΔ inelastic channel. Our predicted inelasticities are in generally good agreement with the data, but are smaller than the predictions of Green and Sainio. The Argand plots of the 1D2, 3F3, 3P1, and 1G4 all show counterclockwise motion resulting from the onset of inelastic channels. 相似文献
10.
For the first time, the recently predicted chemical shift of neutron resonances, to be regarded as an analogue to the Mössbauer isomer shift, has been experimentally observed studying the 6.67 eV resonance of 238U. The experimental shifts were determined by a chi-square fitting technique from the time-of-flight transmission spectra of metallic uranium and four uranium compounds measured at the Dubna IBR-30 pulsed reactor. A computational method has been applied to estimate, and compensate for, the influence of the crystal-lattice vibrations on the experimental values thus obtained. The electron density differences at the nucleus have been calculated for the various sample pairs using available data on chemical X-ray shifts in uranium compounds, on Mössbauer isomer shifts in isovalent neptunium compounds and on free-ion electron densities. The resonance shift results lead to the conclusion that the mean-square charge radius of 238U diminishes by 1.7?0.8+1.2 fm2 upon capturing the resonance neutron. 相似文献
11.
F. Soga Y. Hashimoto N. Takahashi Y. Iwasaki K. Sakurai S. Kohmoto Y. Nogami 《Nuclear Physics A》1977,288(3):504-528
Excitation functions for elastic and inelastic scattering of protons from 110Cd and 112Cd have been measured in the energy ranges of 5.8–8.1 MeV in 110Cd and 6.1–8.4 MeV in 112Cd. Elastic resonance data have been analyzed using the many-level formula of modified R-matrix theory. Angular distributions have been measured at four prominent inelastic resonances- The results are compared with spectroscopic predictions deduced from calculations using the quasiparticle randomphase approximation (QRPA). The contributions of two different modes arising from the 2p-1h character of the analog state and from the particle-core coupling nature of the parent state were deduced in a microscopic picture. The interference between the resonance and direct scattering has a marked effect on the inelastic angular distributions. 相似文献
12.
The reaction 92Mo(t, α)91Nb has been carried out at a triton bombarding energy of 12 MeV. Angular distributions of the emitted α-particles were obtained and compared with DWBA predictions. Relative spectroscopic factors were obtained for six low-lying states and are discussed with reference to shell-model calculations. 相似文献
14.
Analyzing powers and cross sections have been measured for elastic and inelastic scattering of 24.5 MeV protons from 20Ne and 22Ne, and for 16O, 28Si and 32S at 30.3 MeV. The experimental results were analyzed in terms of the coupled-channels formalism using the rotational model and (for 32S and 16O) the vibrational model. The results for 20Ne, 22Ne and 28Si show a systematic trend of the hexadecapole deformation. Prolate shapes for 20Ne and 22Ne and an oblate shape for 28Si are confirmed. The results for 32S are almost equally well-reproduced by the vibrational or rotational model, and there is a slight preference for the prolate shape for this nucleus. The best fits for the analyzing power for all the nuclei were obtained by using the full Thomas form for the spin-orbit potential 相似文献
15.
F. Terrasi A. Brondi P. Cuzzocrea R. Moro G. La Rana M. Romano B. Gonsior N. Notthoff E. Kabuss 《Nuclear Physics A》1983,394(3):405-412
Excitation functions for the 40Ca(p, γ)41Sc reaction have been measured at 0° and 90° in the proton energy range Ep = 2.1–3.1 MeV. The experimental results have been interpreted in terms of the direct capture process to the first excited state of 41Sc. The direct capture transition to the ground state has been observed only at a few proton energies. The spectroscopic factor of the first excited state in 41Sc has been found to be 1.0 ± 0.3. The direct capture cross section to the ground state is consistent with the spectroscopic factor reported from stripping reactions. 相似文献
16.
The effect of the quadrupole transition between the 8Be 4+(11.4 MeV) and 2+(2.9 MeV) states is included in low energy α-α bremsstrahlung (E1ab < 30 MeV). In the equal-angle Harvard geometry this dominates for θ < 30°, and so enables an estimate to be made of B(E2, 4+ → 2+, 8Be). The problem of non-coplanarity is also discussed. 相似文献
17.
The symplectie shell model, which incorporates vertical major shell configuration mixing as dictated by a quadrupole interaction, is augmented with horizontal (0?ω) mixing induced by realistic single-particle energies and a monopole-pairing interaction. The excitation spectrum and B(E2) rates of the 20Ne ground band are accurately reproduced without the use of an effective charge. The degree of horizontal and vertical mixing is found to be on the order of 20% in the ground state and up to as much as 50% for the 8+ level. 相似文献
18.
The (d, 3He) proton pickup reaction on 44Ca has been studied at a deuteron energy of Ed = 19.0 MeV using the Minnesota MP Tandem Van de Graaff. Differential cross sections were measured at forward angles and spectroscopic factors were extracted in the usual fashion for the transitions to five states of 43K. The results are compared with previous proton pickup and stripping reactions on the even Ca isotopes. Only about half of the sd hole state excitation strength observed in the stripping reactions could be found in the pickup from the fp orbitals if the data are analyzed by standard distorted wave calculations. This discrepancy can be removed by using bound state potential radii which are slightly larger for sd orbitals than for fp orbitals. 相似文献
19.
The spins of 15 resonances in the 235U slow neutron cross section lying in the neutron energy range between 0.1 and 15 eV were determined by measuring the transmission of polarized monoenergetic neutrons through a target in which the 235U nuclei were polarized. The magnetic moment of 235U is concluded to be negative. 相似文献
20.