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1.
Closely spaced angular distributions have been measured for the reaction between Eα = 17.39 and 20.5 MeV in a search for 8+ strength in 16O. No evidence of 8+ strength is found, but evidence is found for a narrow 7? resonance at 21.52 MeV excitation. 相似文献
2.
D.E. Gustafson J.Gomez Del Campo R.L. Robinson P.H. Stelson P.D. Miller J.K. Bair 《Nuclear Physics A》1976,262(1):96-112
The structure of 26Mg has been investigated by means of the 12C(18O, α) reaction. Several previously unknown states were populated between excitation energies of 0 to 16 MeV. Excitation functions were measured for 126 states for bombarding energies between 43.2 and 45.9 MeV in 300 keV steps at a lab angle of 7°. The experimental energy averaged differential cross sections were compared with statistical model calculations and good agreement was obtained for the states whose spins and parities were previously established. The statistical model calculations were used to suggest the spins and parities for the rest of the states. In particular, candidates for 6+ and 8+ states were interpreted as members of three rotational bands in 26Mg: the ground-state band, the K = 2+ band based on the 2.938 MeV 2+ state, and a K = 0+ band based on the 3.588 MeV 0+ state. Back bending of the yrast band is observed and it is suggested that it may be due to band crossing of the ground-state and first excited K = 0+ bands. 相似文献
3.
Spectra and angular distributions for the reactions 54, 56, 58Fe(16O, 12C)58, 60, 62Ni (Ex = 0.0–4.5 MeV) have been measured at 50 MeV with an energy resolution of 45–80 keV using a Q3D spectrograph. The selectivity of the (16O, 12C) reaction is found to be very similar to the (6Li, d) reaction. The close correspondence recently noted between the (6Li, d) spectra and levels strongly excited in (t, p) and (3He, n) two-nucleon transfer reactions is also observed to be present for the (16O, 12C) reaction. Relative α spectroscopic factors for (16O, 12C) and (6Li, d) obtained in a DWBA analysis assuming direct one-step α-cluster transfer are in very good quantitative agreement. Unnatural parity states, whose excitation is forbidden in the DWBA α-cluster approximation, are observed to be very weakly populated. These results, together with previous work on s-d shell and Ni targets, strongly suggest that the spectroscopic information provided by the (16O, 12C) and (6Li, d) reactions is essentially the same and that this information may be reliably extracted by DWBA analysis. 相似文献
4.
T. Suehiro J. Kokame Y. Ishizaki H. Ogata Y. Sugiyama Y. Saji I. Nonaka 《Nuclear Physics A》1974,220(3):461-476
The perturbation theory for projected states is applied to the two-level pairing force model. Both approximate and exact forms of number projection are considered. The results are compared with the exact ones and with ordinary perturbation theory based on BCS wave functions without projection. 相似文献
5.
The elastic scattering of 6Li ions from a variety of targets, A = 12 to 208, has been measured at a bombarding energy of 50.6 MeV. The angular distributions are characteristic of strongly absorbed particles, such as 3He and heavy ions, and less diffractive than for 4He. A simple optical model with Woods-Saxon real and imaginary volume potentials is adequate to fit the data. Spin-orbit effects are not apparent in the data. 相似文献
6.
D. Dehnhard W. Saathoff T. S. Bhatia K. Wannebo C. -A. Wiedner 《Zeitschrift für Physik A Hadrons and Nuclei》1979,291(1):71-75
Differential cross sections for18O elastic scattering and the (18O,16C) and (18O,17N) reactions on48Ca were measured at 102 MeV using a Q3D magnetic spectrograph. The transitions to the 7/2? ground state (g.s.) of49Sc and the 0+ (g.s.), 2+ (1.554 MeV), 4+ (2.675 MeV), and 6+ (3.198 MeV) states of50Ti were analyzed by DWBA calculations which include finite-range and recoil effects. Simple cluster-transfer calculations were done for all two-proton transfer transitions. For the 0+ (g.s.) transition a two-nucleon transfer code employing microscopic wave functions was also used. It was found that absolute cross sections for this kinematically well-matched transition were underrated by a factor of about 7 for a reasonable amount of configuration mixing in the nuclear states involved in this transition. This factor is very close to the value 5 derived for the similarly well-matched48Ca(18O,16O)50Ca reaction. 相似文献
7.
A. Weidinger K.A. Eberhard E. Mathiak J. Stettmeier W. Trombik L.N. Wüstefeld 《Nuclear Physics A》1976,257(1):144-164
An array of eight detectors has been developed for identifying the particle unstable 8Be nucleus from nuclear reactions with high detection efficiency. Absolute cross sections have been measured for the reaction 12C(12C, 8Beg.s.)16O to the ground state and to several excited states in 16O. Excitation functions at seven angles from 15° to 45° (lab) in 5° steps have been measured for bombarding energies between E12C(lab) = 35 and 69 MeV. Excitation functions were obtained for the following states in the residual nucleus 16O which were found to be strongly populated: g.s.(0+); 6.1 MeV (0+, 3?); 6.9 MeV (2+); 10.4 MeV (4+); 11.1 MeV (4+); 14.7 MeV (6+,…) and 16.3 MeV (6+,…). The energy range is covered in 250 keV (c.m.) steps; at certain energy ranges in 125 keV or 50keV steps. All excitation functions exhibit a strong energy dependence of the cross section; pronounced gross structures with superimposed fine structures, similar to those observed for 12C+12C elastic and inelastic scattering at these energies, are observed. At 19.3 MeV, where resonant structures were observed in the reactions 12C(12C, p)23Na, 12C(12C, n)23Mg and 12C(12C, d)22Na, no resonance is found for the reaction studied here. At 60, 61 and 63 MeV angular distributions have been measured in 1° and 2.5°(lab) angular steps. The excitation functions have been analyzed in terms of Ericson fluctuations and cross-correlation functions. 相似文献
8.
S. Kubono T.K. Li D. Dehnhard D.A. Lewis J.F. Petersen J.L. Artz 《Nuclear Physics A》1979,313(3):434-444
The structure of the 20O nucleus was studied by the 18O(18O, 16O)20O reaction at E1ab = 52 MeV. Angular distributions for the transitions to the lowest four states in 20O were obtained and analyzed with finite-range DWBA calculations. Optical potential sets were used which fit the experimental elastic scattering differential cross sections over almost the whole angular range. The two L = 0 transitions to the ground state and the 4.45 MeV state of 20O populated by the 18O(18O, 16O) reaction were analyzed with exact finite-range DWBA calculations using microscopic form factors. These calculations underestimate the absolute cross sections by a factor of 11. The relative strength of the two L = 0 transitions is well reproduced in the 18O(18O, 16O) reaction. However, DWBA calculations for the 18O(t, p)20O reaction overestimated the relative cross sections for the excited 0+ state by a factor of 6. Several model wave functions were tested for the ground-state transition. It was found that the absolute cross sections of the (18O, 16O) reaction are very sensitive to the mixing of shell-model configurations. The angular distribution shapes are also slightly dependent on the mixing. 相似文献
9.
The cross section for the reaction 12C(α, γ)16O has been measured for a range of c.m. energies extending from 1.41 MeV to 2.94 MeV, by using 12C targets of high isotopic purity, large NaI(T1) crystals, and the time-of-flight technique for the suppression of prompt neutron background and time-independent background. Gamma-ray angular distributions were measured at c.m. energies of 2.18, 2.42, 2.56 and 2.83 MeV. By means of theoretical fits, which include the coherent effects of the 1? states of 16O at 7.12 MeV, 9.60 MeV, and those at higher energies, the electric-dipole portion of the cross section at astrophysically relevant energies has been determined. A three-level R-matrix parametrization of the data yields an S-factor at Ec.m. = 0.3 MeV, S(0.3 MeV) = 0.14+0.14?0.12 MeV · b. A “hybrid” R-matrix optical-m parameterization yields S(0.3 MeV) = 0.08+0.05?0.04 MeV · b. This S-factor is of crucial importance in determining the abundances of 12C and 16O at the end of helium burning in stars. 相似文献
10.
A measurement of the residues from the 12C + 7Li reaction has been obtained for 7Li energies from 10 to 38 MeV. From these measurements the fusion cross sections and critical angular momenta for the 12C + 7Li system have been deduced. Cross sections for the 7Li(12C, t)16O reaction have been obtained for 12C energies from 54 to 62 MeV at θlab = 2.7°. The critical angular momenta obtained from the fusion cross sections have been used to perform Hauser-Feshbach calculations for the 12C(7Li, t)16O reaction. These calculations have been compared to measured angular distributions over a wide energy range. By comparing the fusion cross sections required by the Hauser-Feshbach calculations to fit the 12C(7Li, t)16O(8.87 MeV) reaction and the measured residue cross section it is estimated that at least 80 % of the measured residues are fusion products. The calculations also indicate that direct processes dominate the population of many 16O levels at forward angles and the 10.35 MeV state at backward angles. The necessity for using a critical angular momentum in Hauser-Feshbach calculations is discussed. 相似文献
11.
J.R. Shepard R.E. Anderson J.J. Kraushaar R.A. Ristinen J.R. Comfort N.S.P. King A. Bacher W.W. Jacobs 《Nuclear Physics A》1979,322(1):92-108
Angular distributions have been measured for the low-lying levels of the residual nuclei for the 12C, 54Fe and 208Pb(p, t) reactions at Ep = 80 MeV. The shapes of these angular distributions are generally well reproduced by the zero-range distorted-wave Born approximation (DWBA). Enhancement factors extracted from the data show that the DWBA predicts relative strengths consistent with those observed at lower bombarding energies. However, the overall empirical DWBA normalization at Ep = 80 MeV is observed to be () of that required at 40 MeV for 208Pb (54Fe). 相似文献
12.
N. Ikeda F. Nakamura K. Mizuuchi T. Sugimitsu S. Teruyama T. Okamoto H. Fujita S. Morinobu 《The European Physical Journal A - Hadrons and Nuclei》2000,7(4):491-502
The 16O(13C,12C)17O reaction at 50 MeV has been investigated using the kinematical coincidence method. Polarization tensors t
20 and t
40 of 12C[2+
1] for the quantization axis taken along the direction of propagation have been measured by analyzing the energy spectrum of
12C[2+
1], modulated by the effect of γ ray emission. The deduced t
40 values significantly deviate from zero, contrary to the prediction of the distorted-wave Born approximation theory based
on one-step p shell neutron stripping without spin-dependent interactions. The phenomenological spin–orbit interaction necessary
to reproduce the magnitude of measured t
40 is found to be much larger than the folding model prediction. It is shown that the experimental polarization tensors as well
as the cross sections can be reproduced by introducing multi-step processes involving excitations in 12C and 13C without introducing spin-dependent interactions.
Received: 2 August 1999 / Revised version: 3 February 2000 相似文献
13.
M. Aliotta S. Cherubim E. Costanzo M. Lattuada S. Romano D. Vinciguerra M. Zadro 《Zeitschrift für Physik A Hadrons and Nuclei》1995,353(1):43-47
The12C+12C→8Be gs +116O gs reaction has been studied at c.m. energies of 27.9, 32.5 and 35.0 MeV. The energy dependence of the cross section is consistent with a resonant behaviour like the one observed for two12C nuclei excited in a very deformed state in the final channel. The angular distributions for the two reactions show also a similar oscillatory behaviour. The analysis suggests that the reaction proceeds through the formation of an intermediate state with a complex nature, involving largely deformed configurations as well as almost spherical ones. 相似文献
14.
Ch. Setzensack H. Hick K. Tanaka H. Morinaga 《Zeitschrift für Physik A Hadrons and Nuclei》1982,307(2):109-112
The58Ni(12C,γ)70Se capture reaction was studied with beam energies ofE 12C=30 to 42 MeV. The capture events were identified by means of the residual activity produced in the reaction. At a beam energy of 38 MeV the capture cross section has been determined to 1.5±0.7 μb. AtE 12C=30, 34 und 42 MeV we established upper limits of 0.3, 0.5 and 0.6 μb, respectively. The experimental results are compared with a statistical model calculation. 相似文献
15.
The reaction 14N(3He, p)16O has been investigated at a bombarding energy of 15.0 MeV, using a differentially pumped gas target. Angular distributions were measured for 30 levels below 16.5 MeV in excitation. Data were compared with shell-model calculations of Zuker, Buck and McGrory for states whose correspondence with theory is established. Many states are found to possess a large compound-nucleus reaction component. Several previously unreported levels are observed at high excitation. Angular distributions for all except the weakest levels have been compared with DWBA calculations. 相似文献
16.
M.C. Mermaz M. Ruscev M. Gai J.F. Ennis K.N. Gamadia J.F. Shriner N. Tsoupas S.M. Sterbenz D.A. Bromley 《Nuclear Physics A》1984,429(2):351-364
The 24Mg(12C, α)32S reaction has been studied in the region of the Coulomb barrier. Three angular distributions for the α-particle groups populating the ground and first-excited 2+ state of 32S have been measured spanning the apparent resonant structure observed at Ec.m = 14.20 MeV. Regge-pole and phase-shift analyses suggest a spin assignment of 8 for the corresponding resonance at Ex = 30.51 MeV in 36Ar. 相似文献
17.
F. Pougheon M. Bernas M. Roy-Stephan C. Détraz D. Guillemaud E. Kashy M. Langevin F. Naulin P. Roussel 《Nuclear Physics A》1981,355(1):207-220
The first measurements are reported for (14C, 12C) two-neutron stripping reactions. Energy spectra up to an excitation energy of 12 MeV have been measured at 69 MeV for the 26Mg(14C, 12C) and 28Si(14C, 12C) reactions. A strong selectivity of this reaction is observed. Using this selectivity, the comparison of the spectra suggests Jπ assignments for several 30Si and 28Mg states. The results from the other two-neutron stripping reactions, (t, p) and (18O, 16O) are compared with those of the (14C, 12C) reaction. 相似文献
18.
J. Cook L.C. Dennis K.W. Kemper T.R. Ophel A.F. Zeller C.F. Maguire Z. Kui 《Nuclear Physics A》1984,415(1):114-126
The elastic scattering of 6Li + 16O at 48 MeV has been measured and fitted with an optical model calculation. Measurements have been made of the 16O(6Li, α)F reaction at 48 MeV populating the 1+ g.s., 3+ 0.927 MeV and 5+ 1.122 MeV states in 18F. The data exhibit cross sections at large angles comparable to those at forward angles, and have been compared with exact finite-range DWBA calculations. Exchange contributions were included for the 1+ g.s. and were unable to account for the large-angle data. Calculated statistical compound nucleus cross sections were approximately a factor of 100 below the data. The same conclusions are reached for previously published data at 34 MeV. 相似文献
19.
Angular distributions for eight proton groups corresponding to states in 13C have been measured at incident 3He energies of 4, 6, 8, 10 and 12 MeV. These states are p0(ground state), P1(3.09), p1(3.68), p3(3.85), p4(6.86), p7(7.68), pio(9.50) and p11 (9.90). The angular distributions have been fitted with DWBA analyses using a zero-range approximation. No radial cut-offs were used. In general the data are reasonably well fit at incident energies of 10 and 12 MeV. 相似文献
20.
A polarized beam was used to measure angular distributions of the analyzing power of the 15N(p, α)C reaction at 0.34 MeV and at five energies from 0.92 to 1.21 MeV. The analyzing power can be fitted with associated Legendre polynomials, P11 and P12 sufficing to describe the results except near 1.2 MeV where P31 is also required. Polarization excitation functions were measured throughout the entire energy range at angles where the polynomials P12 and P13 are zero. A polarization contour map is given. 相似文献