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1.
The angular distributions of the energy spectra of the light charged particles (p, d and α) from the 9Be + 28Si reaction have been measured in the energy range 12 ≦ Elab ≦ 30 MeV. The particle evaporation spectra and the angular distributions were analyzed with a spin dependent statistical model. Angular distributions of 9Be ions elastically scattered on 28Si have been measured at the energies 12 MeV, 17 MeV, 23 MeV and 30 MeV and were analysed, together with previously measured cross sections, with the optical model. The fusion cut-off angular momentum lfus(E), the fusion cross section σfus(E) and the ratio σfus/σROM(E) were deduced. The excitation function for fusion was analyzed with the Glas and Mosel model. The parameters obtained from the fusion excitation function were compared with the corresponding ones from the 9Be + 28Si optical-model interaction potential.  相似文献   

2.
The excitation energies of the levels in 30Si have been measured up to an excitation of 9.46 MeV with the 28Si(t, p)30Si reaction at a triton energy of 6.0 MeV. Angular distributions have been measured of proton groups from the 28Si(t, p)30Si and 29Si(d, p)30Si reactions in a multi-angle magnetic spectrograph. Triton bombarding energies of 10.5 and 12.1 MeV were used and the deuteron incident energy was 10.0 MeV. States in 30Si up to an excitation of 8 MeV were observed. Spins and parities of several states have been assigned using an empirical method for the (t, p) results and using a DWBA analysis for the (d, p) distributions. Spectroscopic factors for twelve states were obtained from the latter analysis. Two of these disagree with theoretical predictions. The state previously reported at an excitation of 6.63 MeV in 30Si was observed to be formed by a strong L = 0 transition in the (t, p) reaction and also by a strong l = 1 transition in the (d, p) reaction. We deduce that there are two closely spaced states at about this excitation, one having a spin and parity of 0+ and the other 0?, 1? or 2?.  相似文献   

3.
Fusion and inelastic scattering coupled-channel calculations are carried out for the systems 18O + 44Ca and 12C + 48Ti. Comparison between 12C + 48Ti and 32S + 24Mg sub-barrier fusion cross-section enhancement is made using simple analytical expressions. The distribution of the angular momentum absorbed by the compound nucleus is discussed in a quantum-mechanical coupled-channel model.  相似文献   

4.
Angular distributions for one- and two-nucleon transfer reactions induced by 16O on 29, 30Si and for the elastic scattering of 16O on 28, 29, 30Si have been measured at 73.5 MeV bombarding energy. The results are analyzed with the DWBA code BRUNHILD that includes recoil effects. Spectroscopic factors extracted for all observed transitions in one-nucleon transfer reactions agree well with those derived from light panicle reactions. The effects of recoil on the Spectroscopic factors for transitions to final states with different spins are discussed. The transitions from smooth to oscillating angular distributions are examined. It is found that the shape of the angular distributions depends on both the matching conditions of the reaction and the localization of the S-matrix amplitudes in L-spacef.  相似文献   

5.
Alpha particles have been measured in coincidence with heavy recoil nuclei from the 28Si + 12C reaction. At Elab = 87 MeV angular correlations for alphas between 15° and 55° and heavy ions at angles ?9°, ?12° and ?15° have been taken. An excitation function of coincidence events with θα = 30° and θHI = ?12° has been measured for 84 MeV < Elab < 91.5 MeV. The results are well described by a statistical-model calculation for compound nucleus decay. No evidence is found for additional processes.  相似文献   

6.
The cross sections for the 10B(13C, 12C)11B neutron-transfer reaction, leading to the 11B 4.45 and 6.74 MeV and 12C 4.44 MeV excited states, and for 13C + 10B fusion have been measured by the characteristic and total γ-ray yield methods, respectively, over the energy (c.m.) interval 2.4–5.8 MeV. For 13C + 11B, with no transfer reactions present, the fusion cross sections have been measured between Ec.m. = 2.3 and 6.4 MeV. The fusion cross sections for 13C + 10B and 13C + 11B are found to be almost equal and slightly enhanced with respect to those for 12C + 10B and 12C + 11B.  相似文献   

7.
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   

8.
Yrast levels of 60Ni were investigated via the study of in-beam γ-rays induced by 15–25 MeV α-partictes on 58Ni, 26–48 MeV 12C ions on 50Cr and 30–60 MeV 16O ions on 46Ti. The compound nucleus formed by these target-projectile combinations is 62Zn, and its decay by two-proton emission populates yrast levels of 60Ni. The ordering and decay modes of the yrast levels were determined from the analyses of in-beam γ-ray angular distribution and γ-γ coincidence measurements. The new levels established are at 4.262, 5.345 and 6.807 MeV. These together with the known 21+ (1.332 MeV) and 41+(2.505 MeV) levels constitute the yrast cascade. The spin assignments based on the present study are 6, 7, 9 for the 4.262, 5.345 and 6.807 MeV levels, respectively. The excitation functions for the yrast γ-rays from the 50Cr(12C, 2p)60Ni reaction show peaks near 33 MeV incident energy.  相似文献   

9.
The yield of γ-rays from the reaction 46Ti(p, γ)47V has been measured as a function of bombarding energy over the range 0.72–3.00 MeV, from 47Ti(p, γ)48V over the range 0.74–3.50 MeV, and from 48Ti(p, γ)49V over the range 0.72–4.40 MeV. The yields of γ-rays following (p, p') reactions on all three targets were also measured and (p, p') cross sections were deduced for the first excited state proton groups for 46Ti and 48Ti and for the first ten proton groups for 47Ti. The yield of neutrons from the reaction 47Ti(p, n)47V has been measured over the range from threshold to 4.40 MeV. All these data are compared with statistical-model calculations, and good agreement is achieved. Thermonuclear reaction rates for the (p, γ) and (p, n) reactions are calculated for the temperature range 5 × 108–1010 K which includes the range of temperatures of interest in nucleosysnthesis calculations.  相似文献   

10.
The energy dependence of the fusion cross section has been measured over the range Ec.m. = 3.05–6.88 MeV by detecting the γ-rays from residual nuclei in a 4π geometry. Analyzing the 1.37 MeV photopeak, originating from 24Mg 1.37 MeVg.s. transition, the cross sections for 24Mg+2n channel were also deduced. The measured fusion cross sections have been compared with those for 12C + 12C and 12C + 13C systems and found to be significantly different. For 13C+13C the fusion cross sections agree with the standard optical-model prediction down to the lowest measured energies, while for 12C + 12C and 12C + 13C they are, at the lowest energies, too low. It is suggested that the unpaired valence nucleons facilitate fusion at energies well below the Coulomb barrier.  相似文献   

11.
Absolute cross sections for nuclei produced in the reactions 46–50Ti + 13C at 36, 46 and 56 MeV (lab) were measured. Complete identification in mass and atomic number for the evaporation residues was obtained by means of in-beam γ-ray spectroscopy techniques. In the entire energy range, an overall satisfactory account of the observed product nuclei is given by the predictions of the fusion-evaporation model. Direct channels like inelastic scattering and n-transfer appear to be noticeable and contribute ~ 15 % to the total cross section.  相似文献   

12.
By using the γ-ray-multiplicity technique, experiments were carried out to determine the input angular momenta lin corresponding to the heavy-ion induced incomplete-fusion reactions involving the emission of fast charged particles. The α-particle and Li-nuclei emission channels were investigated in the reaction 181Ta + 22Ne at the average Ne-ion energy of 155 MeV and for the α-particle emission channel in the reaction natIr+12C at E = 100 MeV. The separation of the reaction channels was carried out using an X-ray spectrometer. The angular distributions of the fission fragments were measured in the reaction 181Ta(22Ne, αf). The data obtained indicate that input angular momenta are equal to about 60 ? and 50 ? for the channels of Li emission and α-emission, respectively, being practically independent of the particle energy. For the α-emission channel the lin values are the same for both reactions within experimental errors. The lifetime of the system of interacting target and projectile nuclei, prior to the emission of an α-particle, has been estimated to be equal to 10?20s.  相似文献   

13.
The mass excesses of 33Si and 34Si have been measured using the 36S(11B, 14, 13N)33, 34Si; reactions. Values of ?20.550 ± 0.030 MeV (33Si) and ?20.017 ± 0.025 MeV (34Si) were obtained. In addition, an excited state of 34Si was observed at 5.33 ± 0.05 MeV, and excited levels of 33Si were observed at 1.06 ± 0.02 and 4.32 ± 0.03 MeV. These results are compared with recent shell-model calculations.  相似文献   

14.
The 30Si(30He, t)30P reaction has been measured for about 100 levels in 30P with Ex < 8.8 MeV. Little selectivity in the population of states has been observed. For 75 levels angular distributions have been analysed using a “fingerprint method” by determining the L-value from a comparison in shape with transitions to states with known Jπ. For possible mixed L-transitions a dominance of the higher L-value is observed for almost all cases. Coulomb displacement energy calculations utilizing shell-model wave functions have been used to identify T = 1 states.  相似文献   

15.
The 13C(6Li, t)16O reaction has been studied at 34 MeV. Selective population of narrow states is observed up to 21 MeV excitation in 16O. This reaction populates strongly both unnatural-and natural-parity states that have little or no 12C + α0 width. The measured angular distributions are compared with Hauser-Feshbach and finite-range DWBA calculations. Reasonable agreement with the DWBA calculations is found for most of the states strongly populated. The widths of the narrow states populated in the 16–20 MeV excitation region are presented. Comparison of the present data with that from medium-energy inelastic scattering and other multiparticle transfer reactions is made.  相似文献   

16.
Distributions of cross sections and analysing powers have been measured over the range ~ 14°–100° c.m. for the (3H, 3He), (3H, 4He), (3H, 2H) reactions at 33.4 MeV incident e using a ~ 95 % enriched 30Si target. Phenomenological optical-model analyses of the elastic-scattering data have been carried out. A DWBA analysis of the inelastic-scattering data for the 2.24 MeV (2+) and 5.49 MeV (3?) states of 30Si has yielded values of the deformation β2 and β3. The j-dependence of the analysing powers for the (3He, 4He) and (3He, 2H) reactions has identified the 6.71 MeV level of 29Si as a 52+ state, and a level near 9.5 MeV in 31P as a possible 72? state. Spectroscopic factors for ten states in 29Si and seven states in 31P have been deduced and are compared with other work. The extent to which the data defines the 3He spin-orbit potential is discussed.  相似文献   

17.
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 32+ state at 0.97 MeV which displays a marked departure from the bell-shaped angular distribution obtained for the other 32+ state at 2.80 MeV, and the 72+ 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   

18.
D. Baye 《Nuclear Physics A》1976,272(2):445-465
An angular momentum projected microscopic calculation is performed for the 12C + 16O system with an effective nuclear force and the exact Coulomb interaction. The 12C wave function is projected on a 0+ state. Parametrizations of the Coulomb interaction between the nuclei are fitted. The L-projected energy curves present a quite complicated structure especially for the negative parity states. The role played by critical angular momenta is put into evidence. A generator coordinate calculation gives several bands of bound, quasibound and virtual states. Excellent agreement in energy and angular momentum is obtained with the 13.7 MeV (J = 9), 19.7 MeV (J = 14), 22.7 MeV (J = 15) and other resonances.  相似文献   

19.
The polarization of 21 MeV 3He elastically scattered from 27Al and 28Si has been measured in an angular range of θlab = 25°–55°. Differential cross-section data have been obtained out to angles of approximately 100°. The small values observed in the polarization distributions differ somewhat from optical-model predictions based on fits to the differential cross-section data and cannot be used to obtain significant information about the optical-model spin-orbit potential. It is concluded that statistically significant, non-zero 3He polarization measurements will not be possible using traditional double scattering techniques for 3He energies ≦ 27 MeV and targets of Z ≧ 13.  相似文献   

20.
The excitation functions of the 20Ne(12C, p)31P, 20Ne(12C, d)30P. and 20Ne(12C, α)28 Si reactions were measured at bombarding energies between 6.9 and 16.9 MeV (c.m.) by steps of 156 keV, at an average lab angle of 2.82°. The average coherence width of states in the compound nucleus, 32S, populated in the reactions was deduced through the analysis of the fluctuations in the measured excitation functions. The result agrees with the average compound nucleus width predicted by the Hauser-Feshbach expression. The fluctuation analysis shows that these reactions proceed mainly through the formation of a compound nucleus. A cross correlation analysis revealed that the fluctuations in the different excitation functions are statistically independent and that there is no evidence of intermediate structure resonances.  相似文献   

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