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1.
Angular distributions of neutron polarization from the 14C(p, n)14N and 11B(α, n)14N reactions have been studied for the particle energies Ep = 1.788, 2.025, 2.272 and 2.450 MeV, and Eα = 2.049 MeV. The polarization was derived from the left-right asymmetry induced by elastic scattering from 4He. Together with existing measurements of angular distributions and total cross sections for several reaction channels leading to 15N with an excitation energy between 11.5 and 12.5 MeV, these data were used to deduce from R-matrix analysis a set of resonance parameters for the 15N levels in this energy range. 相似文献
2.
Nuclear reactions between 19F and 12C target nuclei were studied at beam energies of 50, 63.2 and 76 MeV. Reaction products in the mass range from A = 11 to 31 emitted in forward direction (4°–20°) were identified with a time-of-flight telescope. Mass distributions of the fusion products were obtained. Their characteristic structure is interpreted as a consequence of the superposition of nucleon and α-particle emission. Qualitative conclusions are drawn on the relative intensities of the different decay modes of the compound nucleus. Fusion cross sections and estimates of the contribution of direct channels to the total reaction cross section are discussed. 相似文献
3.
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
4.
A. Cunsolo A. Foti G. Immè G. Pappalardo G. Raciti N. Saunier B.T. Kim 《Nuclear Physics A》1981,355(1):261-268
Angular distributions of the charge exchange reaction 14C(6Li, 6He)14N leading to the 1+ ground state and 3.95 MeV 1+, and 5.20 MeV 2? excited states at the 34 MeV incident beam energy were analyzed and measured. The 62 MeV data of Goodman et al. were also reanalyzed. The direct one-step charge exchange caused by the spin-isospin dependent term in the two-body interaction can account well for the observed data. The strength of spin-isospin dependent effective interaction (gaussian form with a range parameter of 1.8 fm) was extracted to be 18.5 MeV. 相似文献
5.
6.
K.R. Cordell S.T. Thornton L.C. Dennis T.C. Schweizer J.Gomez Del Campo J.L.C. Ford 《Nuclear Physics A》1978,296(2):278-288
The 12C(14N, α)22Na reaction was studied at bombarding energies between 22 and 39.2 MeV (lab) and a lab angle of 7°. Average coherence widths of states in the compound nucleus 26Al populated in the reaction were obtained from excitation functions of twenty states or unresolved multiplets measured for states in 22Na. From these data and Hauser-Feshbach predictions, values were determined for the level density parameters and for the effective moment of inertia of 26Al. The critical angular momentum for the reaction was determined by comparing ratios of cross sections for excited states of 22Na with Hauser-Feshbach predictions. 相似文献
7.
Angular distributions of protons from the 12C(α, p)15N reaction have been measured over the angular range from 10–70° at an α-particle bombarding energy of 96.8 MeV. Well defined particle groups are observed up to an excitation energy of 18 MeV in 15N. The relatively small number of states excited implies a selectivity both in the reaction mechanism and in structure effects. DWBA calculations using a semi-microscopic three-nucleon form factor have been performed using several different sets of wave functions. Good agreement in the ratio σexp/σth is obtained for most states using the 15N wave functions of de Meijer. The strongest state in the (α, p) spectrum is observed at 15.397 MeV in 15N and DWBA calculations give good agreement for a assignment. This state has been observed only in other three-nucleon transfer reactions involving heavy ions. The recent discovery of a state at 10.693 MeV in a p+14C resonance measurement is supported by our analysis. 相似文献
8.
Angular distributions of cross section and vector analyzing power have been measured for the 14N(d, p)15N reaction at Ed = 10 MeV for transitions to levels up to 8.6 MeV excitation in 15N. Distorted wave Born approximation calculations and calibration curves were used to determine total and orbital angular momenta and spectroscopic factors of the transferred neutrons. The results were compared with different theoretical approaches. 相似文献
9.
Two broad resonances at 9.33 MeV and 9.65 MeV are observed in the inelastic excitation of 18O on a 12C target at a laboratory energy of 82 MeV. The α-decay of these states has been measured. A coherent sum of Jπ = 2+ and 3? is required to fit the correlations. The structure of these states and the excitation mechanism is discussed. 相似文献
10.
D. Konnerth W. Trombik K.G. Bernhardt K.A. Eberhard R. Singh A. Strzalkowski W. Trautmann 《Nuclear Physics A》1985,436(3):538-560
We have studied elastic scattering, inelastic scattering and several transfer channels of the systems 14C + 14C and 14C + 12C over a wide range of energies up to Ec.m. = 35 eMeV and 32 MeV, respectively. The reaction channels were identified by means of kinematic coincidences between solid-state detectors, γγ coincidences were measured to determine cross sections for mutual inelastic scattering of 14C + 14C.Pronounced regular gross structures, similar to those found for 16O + 16O, are observed in the elastic excitation function of 14C + 14C at θc.m. = 90°, The angular distributions measured at the energies of the maxima and an optical-model analysis suggest that one or a few surface partial waves dominate the scattering behaviour. Correlated structure of narrower width is found in the inelastic channels and, to a lesser degree, in the transfer channels which appear with rather small cross sections.In 14C + 12C elastic scattering the gross structures are strongly fragmented, in contrast to 14C + 14C but similar to 12C + 12C. While the 12C(2+) excitation is very weak, the observed strengths of the 14C(3?) excitation and of neutron transfer point to a substantial role of these channels as coupling partners to the elastic configuration and to their influence on the elastic scattering behaviour. A correlated intermediate structure is observed near 23.5 MeV, where a dominance of l = 18 is suggested by the elastic scattering angular distribution. This unexpectedly high l-value exceeds lgraz at this energy by at least two units of ?. 相似文献
11.
Energy and angular distributions of neutrons from the reaction 14C(d, n)15N have been measured at 6.5 MeV deuteron energy. The DWBA analysis yielded l-values and absolute spectroscopic factors for fifteen states in 15N below 10 MeV excitation energy. For the 9.23 MeV level Jπ is determined to be + or +, for the 9.93 MeV level the data suggest . The spectroscopic factors are in qualitative agreement with pure jj coupling and in semi-quantitative agreement with shell-model calculations. 相似文献
12.
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
13.
Energy spectra and differential cross sections of nitrogen products formed in the reaction 28 MeV 11B + 12C have been measured using a ΔE?E counter telescope. The energy spectra are smooth and therefore indicate that the nitrogen products were formed by a compound nucleus mechanism, via the formation and decay of the compound nucleus 23Na. The experimental results are compared with statistical model calculations and good agreement is obtained. This result provides further evidence for the importance of the compound nucleus mechanism in heavy ion reactions with light nuclei and also gives added validity to the statistical model for light compound systems. 相似文献
14.
Gamma rays in the range 5.4–6.7 MeV have been studied for 31 s-wave neutron resonances of 115In, selected by time of flight in the range 3–430 eV. In a subsidiary experiment, spin J = 5 has been assigned to 17 and J = 4 to 14 resonances by measuring intensity variations of some strong low-energy transitions. The reduced widths averaged over all initial states of the same spin have been estimated for 41 primary transitions: these values have provided information on the spin and parity of the corresponding 116In final states. Overall mean values of E1 and M1 radiative strength have been calculated. The width distribution has been fitted with a χ2 function with ν = 1.10+0.27?0.09 degrees of freedom for M1 and ν = 1.42 + 0.014?0.08 for E1 radiation. An estimate of the spin cut-off parameter σ = 3.6?0.4+ 0.8 has been derived. A non-statistical effect already evidenced in previous measurements has been confirmed, consisting of a strong modulation of the radiative strength against resonance energy, correlated also with the local neutron strength function. In addition, it has now been shown that this structure is due to E1 radiation only. 相似文献
15.
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
16.
The second order processes in particle transfer reactions are tested by measuring the resonance structure of the 3+ state of 14N at 12.61 MeV for some outgoing channels of the 12C + d reaction. 相似文献
17.
F. Rigaud G.Y. Petit J. Dalmas J.L. Irigaray M. Suffert F. Saporetti G. Longo R. Guidotti 《Nuclear Physics A》1979,326(1):26-36
Spectra of high-energy photons following the radiative capture of 8–22 MeV protons in 110Cd and 111In are measured. The (p, γ) differential cross sections at 90° with respect to the beam axis is deduced from the integration of measured spectra. The photon angular distribution is measured for the reaction, too, at 13 MeV incident energy. Satisfactory agreement between theory and experiment is obtained by using the direct-semidirect model for dipole and quadrupole fast nucleon radiative capture. 相似文献
18.
K. Baba I. Endo H. Fukuma K. Inoue T. Kawamoto T. Ohsugi Y. Sumi T. Takeshita S. Uehara Y. Yano T. Maki 《Nuclear Physics A》1984,415(3):462-476
Momentum spectra of protons emitted at three lab angles 23°, 55° and 130° in high-energy photoreactions of 9Be and 12C are studied by using tagged photons in the energy range between 360 and 600 MeV. At 23° and 55°, we observe a structure which may be ascribed to protons from quasifree production of a single pion and those from quasideuteron photodisintegration, while at 130°, the spectra are predominantly due to protons resulting from intranuclear multiple scattering. The results of an intranuclear cascade calculation are compared with the data. 相似文献
19.
Quasi-complete in-plane correlations are measured between two heavy fragments (12C, 12C; 12C, 13C) which leave a missing mass such as n, p, d or p + n in 14N + 12C at 48 MeV. The use of two position-sensitive telescopes in coincidence allows an observation of data over 675 combinations of angles. The strongest coincidence yield concerns the 12C + 13C + p exit channel in which the target (12C) is left either in its ground state or in its first excited state ( respectively). No significant yield is found for the dissociations 12C + 12C + d, 12C + 13N + n or 12C + 10B + α at this energy.Using the reconstructed proton velocities, we obtain a source pattern in the rapidity plot which is roughly centered in the so-called mid-rapidity region. On the other hand, the Dalitz plot exhibits an enhancement of events which could be due to a projectile fragmentation via a real or virtual excitation energy of 8.7 MeV. 相似文献
20.
The 13C(3He, d) reaction at a beam energy of 43.6 MeV was used to examine levels of 14N up to 11.7 MeV over an angular region including the main stripping peaks. Many spectroscopic factors were determined reliably for known states and found to be mostly in good agreement with calculations for the stronger levels. Several new spin or parity assignments are made at high excitation. 相似文献