共查询到20条相似文献,搜索用时 15 毫秒
1.
K.G. Bernhardt H. Bohn K.A. Eberhard R. Sielemann R. Vandenbosch M.P. Webb 《Nuclear Physics A》1981,365(1):157-172
Excitation functions for α-emission leading to the ground and first excited states of 26Mg and 8Be emission leading to the ground and first and second excited states of 22Ne have been measured at several forward angles for Ec.m. = 15 to 22.4 MeV. There is little evidence for correlated structure. The angular distribution at 16.5 MeV for the α + 26Mg(g.s.) channel is rather structureless while that for the 8Be+22Ne(g.s.) channel appears to be dominated by a J = 13 contribution. Statistical model calculations indicate that much of the yield for both the α and 8Be exit channel is compound nuclear in origin, with some indication of a larger direct contribution for the 8Be channel at the lower end of the bombarding energy range. 相似文献
2.
D. Bachelier J.L. Boyard T. Hennino H.D. Holmgren J.C. Jourdain P. Radvanyi P.G. Roos M. Roy-Stephan 《Nuclear Physics A》1976,268(3):488-512
Sixfold energy spectra have been measured for the (p, pα) reaction at 157 MeV on 24Mg, 28Si, 40Ca and 58Ni around quasi-free kinematic conditions. For the three s-d shell nuclei the experiment covered a map ranging from 0 to 220 MeV/c in recoil momentum and from 0 to 20 MeV in excitation energy of the final nucleus. Recoil momentum distributions have been obtained for the 0+ ground state and the 2+ first excited state of 20Ne, 24Mg and 36Ar, and also for the states around 4.4 MeV (mainly 4+) of 36Ar. The a spectroscopic factors extracted by a DWIA analysis are about three times larger than those predicted by the SU(3) model; however, they agree quite well in relative magnitude for a number of cases. The disagreement in shape between experiment and theory observed at low recoil momentum for the 2+ states might result from another reaction mechanism. The cross sections for 58Ni are about a factor often smaller than those for 40Ca. The 58Ni(p, pα)54Fe reaction seems to lead mainly to excited states of the final nucleus. 相似文献
3.
A. Etchegoyen D. Sinclair S. Liu M.C. Etchegoyen D.K. Scott D.L. Hendrie 《Nuclear Physics A》1983,397(2):343-364
The reaction 26Mg(12C, 12B)26A1(5+, 3+) has been studied using a beam of 102 MeV of 12C. Shell-model, microscopic direct model and finite-range coupled reaction channel (CRC) calculations including recoil effects, have been performed, for comparison with the experimental data. DWBA calculations were performed for the intermediate states of interest in the 11B + 27Al and in the 13C + 25Mg channels and these results were also compared with the experimental ones. The dominant reaction mechanism for 26Mg(12C, 12B)26Al(5+, 3+) appears to be the sequential mode. 相似文献
4.
The inelastic α-scattering reaction at Eα = 120 MeV with an energy resolution of 90–150 keV has been used to investigate isoscalar strength distributions in 24, 26Mg, 28Si and 40Ca. For 24, 26Mg and 28Si the E2 strength between Ex = 14 and 27 MeV is strongly fragmented. In 40Ca the E2 strength is mainly concentrated near MeV, although here the onset of fragmentation can be observed. The sum rule strength for the different multipolarities was obtained by applying for each nucleus an L-dependent normalization procedure. In this way we observed in total in 24, 26Mg, 28Si and 40Ca for excitation energies up to 27 MeV an amount of (61+8?6), (50+9?8), (38+8?6) and (94 ± 14)%, respectively, of the isoscalar E2 energy weighted sum rule (EWSR) of which (36+7?5), (28+8?7), (24+7?5) and (74 ± 12)% was found between Ex = 14 and 27 MeV. In addition isoscalar E0, E3 and E4 strength was observed in this excitation energy region. A detailed comparison has been made between the isoscalar quadrupole strength distribution observed in the 24, 26Mg(α, α') reaction and the E2 strength excitation function obtained from radiative α-capture measurements. In the low excitation energy region coupled channel effects have been observed, especially for the excitation of the 3+ states. Moreover, a considerable percentage of the 1?ω isoscalar dipole and octupole strength has been observed for excitations below 14 MeV. 相似文献
5.
A.F. Zeller G.T. Hickey D.C. Weisser D.F. Hebbard B.A. Robson 《Nuclear Physics A》1978,301(1):130-140
Reactions induced by 14N on 26Mg at bombarding energies of 60–95 MeV have been studied. Angular distributions for states populated in 29Si by the (14N, 11B) reaction and in 30Si by the (14N, 10B) reaction have been compared with Hauser-Feshbach and DWBA calculations to determine the reaction mechanism and to deduce spectroscopic information. The cross sections for the states populated in 29Si and 30Si are in poor agreement with statistical model calculations, indicating a non-compound nucleus mechanism. 相似文献
6.
A study of the 12C(9Be, n)20Ne reaction has been carried out at bombarding energies of 16 and 24 MeV. The spectra at both incident energies are dominated by a consistent set of levels between an excitation energy of 7.3 ± 0.4 and 15.7 ± 0.3 MeV. The rotational band based on the Kπ = 03+ state appears to be strongly populated. Based on this selectivity, additional evidence is provided in favor of identification of the 8+ state at 15.9 MeV with this 03+ band. Angular distributions measured at the higher bombarding energy are compared with statistical compound-nuclear calculations. It appears that a non-statistical mechanism is responsible for the reaction's selective population of states with 8p-4h configuration. Such a mechanism, involving the preferential breakup of the 9Be into 8Be plus a neutron, is discussed. 相似文献
7.
8.
A magnetic spectrometer was used for the momentum analysis of pions produced by 185 MeV protons on a 9Be target. The obtained energy resolution (0.55 MeV FWHM) made it possible to resolve a number of discrete final states in 10Be and 10C. Energy spectra were measured in the angular region 15°–130° (lab). Angular distributions for six peaks in 10Be and four peaks in 10C are presented in tables and graphs. A peak corresponding to a not previously reported level in 10Be was observed at 11.75 ±0.11 MeV excitation energy. The measured ratio for the ground state analogues was found to be angular dependent and varied from 30 at 35° (lab) to 2 at 125° (lab). The results are compared with theoretical predictions and discussed in terms of one- and two-nucleon models. 相似文献
9.
The 24Mg(13C, 12C)25Mg reaction has been studied at 30 MeV using a magnetic spectrometer. Differential cross sections for transitions to several final states in 25Mg have been measured and analysed using an exact finite range DWBA code. The DWBA predictions have fitted the bell-shaped distributions satisfactorily, yielding spectroscopic factors which are in reasonable agreement with those obtained using (d, p) reactions. The exceptions are the + state at 0.97 MeV which displays a marked departure from the bell-shaped angular distribution obtained for the other + state at 2.80 MeV, and the + state at 1.61 MeV whose angular distribution has an unusual shape, displaying a deep minimum located at the grazing angle. A semiquantitative model has been used to suggest that the angular distribution for the 0.97 MeV state is evidence for the coupling of inelastic processes in this transition. In the case of the 1.61 MeV state it is suggested that the angular distribution shows the influence of indirect Coulomb excitation on the transfer cross sections. 相似文献
10.
11.
The nucleus 11B has been studied over the excitation energy range from 8.5 MeV to 21.5 MeV with the 9Be(3He, p)11B / reaction at / E3He = 38 MeV. The analogs of the parent states in 11Be have been located at 12.56, 12.92, 14.40, 16.44, 17.69, 18.0, 19.15 and 21.27 MeV. A complementary measurement with the 9Be(α, d)11B reaction at Eα = 48 MeV demonstrates that the 16.44, 17.69, 18.0 and 19.15 MeV resonances have rather pure isospin . The 14.40 MeV state is a strongly isospin-mixed analog of the state in 11Be. It is argued that spin S = 1 transfer is involved in the excitation of the 16.44 MeV state and its 3.887 MeV parent in 11Be in a two-step stripping process. The states and the lowest three states are compared with the predictions of DWBA utilizing shell-model form factors. It is concluded that the strength is more strongly fragmented than is implied by the calculations of Teeters and Kurath. 相似文献
12.
T. Tanabe K. Haga M. Yasue K. Sato K. Ogino Y. Kadota M. Tochi K. Makino T. Kitahara T. Shiba 《Nuclear Physics A》1983,399(1):241-258
The 24, 26Mg(6Li, d)28, 30Si reactions have been studied at 73 MeV bombarding energy. The angular distributions were analyzed with exact finite-range distorted wave Born approximation calculations assuming a direct α-cluster transfer. Extracted spectroscopic strengths leading to low-lying levels of 28Si and relative spectroscopic strengths between transitions to 28Si and 30Si ground states are consistent with those previously obtained by several α-transfer reactions. Many strongly populated levels have been observed at Ex ? 10 MeV for 28Si. A marked similarity was found between the deuteron spectrum and the 24Mg(α, α)24Mg excitation function in this excitation energy region. A brief comparison of the present α-transfer results with previous two-nucleon transfer data leading to 28,30Si is also presented. 相似文献
13.
Data for the (d, 6Li) reaction on targets of 24Mg, 26Mg and 28Si have been obtained at 35 MeV bombarding energy. Angular distributions were measured for low-lying states in the residual nuclei. Zero-range distorted-wave Born approximation (DWBA) calculations have been used to analyze the data. The DWBA calculations account for the shapes of the experimental distributions reasonably well. The observation of significant population of unnatural parity states implies, however, that other transfer mechanisms may be important. The experimental spectroscopic factors are in qualitative agreement with those obtained from SU(3) theory. 相似文献
14.
Gamma-rays following the β? decay of 26Na have been measured with a Ge(Li) detector. The 26Na sources were produced by fast neutron bombardment of an enriched 26Mg sample. Evidence for eight previously unreported β? branches in the disintegration of 26Na has been deduced and their log ft values determined. The half-life of 26Na was measured to be 1.05 ± 0.02 s. Allowed β? transitions (log ft = 4.7 and 6.1 respectively) to the 1.81 MeV, 2+, and to the 4.90 MeV, 4+, levels of 26Mg determine Jπ = 3+ for the 26Na ground state. 相似文献
15.
Joachim Jänecke 《Nuclear Physics A》1973,204(3):497-515
The nuclear structure of the nucleus 25Na has been studied with the (d, τ) proton pick-up reaction on 26Mg at a bombarding energy of 29 MeV with an energy resolution of 25 to 30 keV FWHM. Excited states in 25Na have been measured up to excitation energies of 8 MeV. The experimental angular distributions show good agreement with the predictions from the standard distorted-wave Born-approximation theory (code DWUCK; non-local and finite range). However, the agreement is improved considerably if the procedure of Kunz, Rost and Johnson is applied which accounts approximately for strong couplings to inelastic channels in the initial and final (strongly deformed) nuclei. The influence of this treatment on the evaluation of spectroscopic factors has been investigated and was found to be particularly pronounced for l = 0 transitions. The measured spectroscopic factors are compared to those from other experimental work and from shell-model and Nilsson-model calculations. 相似文献
16.
Z. Y. Tian Y. L. Ye Z. H. Li C. J. Lin Q. T. Li Y. C. Ge J. L. Lou W. Jiang J. Li Z. H. Yang J. Feng P. J. Li J. Chen Q. Liu H. L. Zang B. Yang Y. Zhang Z. Q. Chen Y. Liu X. H. Sun J. Ma H. M. Jia X. X. Xu L. Yang N. R. Ma L. J. Sun 《中国物理C(英文版)》2016,40(11):111001-111001
A cluster-transfer experiment of 9Be(9Be,14C→α+10Be)α at an incident energy of 45 MeV was carried out in order to investigate the molecular structure in high-lying resonant states in 14C. This reaction is of extremely large Q-value, making it an excellent case to select the reaction mechanism and the final states in outgoing nuclei. The high-lying resonances in 14C are reconstructed for three sets of well discriminated final states in 10Be. The results confirm the previous decay measurements with clearly improved decay-channel selections and also show a new state at 23.5(1) MeV. The resonant states at 22.4(3) and 24.0(3) MeV decay primarily into the typical molecular states at about 6 MeV in 10Be, indicating a well developed cluster structure in these high-lying states in 14C. Further measurements of more states of this kind are suggested. 相似文献
17.
E. Ungricht D. Balzer M. Hugi J. Lang R. Müller L. Jarczyk B. Kamys A. Strzalkowski 《Nuclear Physics A》1979,313(3):376-384
The elastic scattering of 9Be on the target nuclei 9Be, 12C, 13C and 16O was measured at projectile energies of 14, 20 and 26 MeV. All angular distributions show a diffraction-like structure. In addition, excitation curves were measured for the scattering of 9Be on 9Be at three different angles in the energy range of 9–22 MeV. An optical potential having parameters independent of mass number and energy and reproducing all the measured angular distributions in the forward angular region was found and compared with that for the scattering of 9Be on medium and heavy nuclei. 相似文献
18.
T. Yamaya K. Umeda T. Suehiro K. Takimoto R. Wada E. Takada M. Fukada J. Schimizu Y. Okuma 《Physics letters. [Part B]》1980,90(3):219-223
The (d, 6Li) reaction was studied at Ed = 54.25 MeV on the target nuclei 12C, 16O, 24Mg, 40Ca and 58Ni. The data were analyzed with finite-range DWBA calculations. The absolute values of the α-cluster spectroscopic factors and the target mass dependence of the relative Sα were in agreement with those in the (p, pα) reaction at Ep = 100 and 157 MeV. The theoretical calculations of the relative Sα were in better agreement with the experimental data at higher energy than at the lower energies. 相似文献
19.
C. Volant M. Conjeaud S. Harar S.M. Lee A. Lépine E.F. Da Silveira 《Nuclear Physics A》1975,238(1):120-140
States in 20Ne have been studied through the 12C(14N, 6Li)20Ne reaction. Excitation functions have been measured from 20 MeV to 60 MeV in steps of 5 MeV at different angles for 20Ne states up to 10 MeV excitation energy. States of 24Mg have been also populated using the 12C(14N, d)24Mg reaction; excitation functions of 24Mg states up to 9 MeV excitation energies as well as angular distributions at 35 MeV bombarding energy have been obtained. Comparisons of data with Hauser-Feshbach calculations show clearly that the compound nucleus mechanism is the main process for both 12C(14N, 6Li)20Ne and 12C(14N, d)24Mg reactions. Strong evidence has been provided for inhibition of the 26Al compound nucleus formation for angular momenta higher than critical values. The location of the yrast line in the 26Al nucleus is discussed. 相似文献
20.
Absolute differential cross sections for the 13C(d, n)14N reaction were measured at deuteron bombarding energies of 4.5, 5.0 and 5.5 MeV. Spectroscopic factors and statistical compound-nucleus contributions are obtained by treating the observed cross sections as an incoherent sum of distorted-wave Born approximation and compound-nucleus contributions. Energy-averaged spectroscopic factors are derived. An anomaly is observed in the yield for the 2.313 MeV T= 1 state. 相似文献