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1.
Angular distributions of the analyzing power in 9Be(p,p)9Be have been measured to an accuracy of about ±0.03 at 21 energies from 0.9 to 2.7 MeV with a target thickness of 20 keV at 1 MeV. These data and the cross section measurements of others are reproduced well in the region from 0.8 to 1.6 MeV by a set of phase shifts that vary reasonably with energy. The 3S1, 5S2, 5P1, and 5P2 phases suffice to describe the data, although channel spin and s-d mixing are required. Three levels satisfy the data: at 0.980±0.010 MeV are two levels, a 1+ of width 0.10 MeV and a 2? of width 0.11 MeV; at 1.37±0.02 MeV is a 1? level of width 0.30 MeV. The 1+ and 1? states do not agree with earlier assignments. Outside of the energy region from 0.8 to 1.6 MeV a satisfactory set of phases could not be obtained, owing to inadequate data. These regions were studied in the analysis, however, and the results are discussed.  相似文献   

2.
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 Tf = 32. The 14.40 MeV state is a strongly isospin-mixed analog of the 52+1.78 MeV 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 Tf = 12 states and the lowest three Tf = 32 states are compared with the predictions of DWBA utilizing shell-model form factors. It is concluded that the Tf = 12 strength is more strongly fragmented than is implied by the calculations of Teeters and Kurath.  相似文献   

3.
Differential cross sections were measured for the reactions 9Be(α, α')9Be, 9Be(α, t)10B and9Be(α, 3He)10B at Eα = 65 MeV for angles ranging from θlab = 6° to 48°. Optical-model analysis was performed for elastic α-scattering from 9Be at Eα = 48, 65 and 104 MeV, and DWBA and CC calculations were done for the inelastic α-scattering at Eα = 65 MeV. DWBA calculations for the 9Be(α, 3He) reactions do not fit the transfer data so well and extracted spectroscopic factors are in disagreement with those of Cohen and Kurath and with values obtained from other reactions. Full CRC calculations assuming a band structure for the low-lying states of 10B and employing a modified set of Cohen and Kurath spectroscopic factors yield globally better fits both in shape and in absolute cross section for differential cross sections to low-lying states in 10B obtained in 9Be(α, t)10B at Eα = 65 MeV and9Be(3He, d)10B at Ed = 17 MeV. In general, strong coupled-channel effects mainly affecting the distorted waves are observed both in entrance and exit channels.  相似文献   

4.
5.
The elastic and inelastic scatterings of 35.5 MeV 4He ions from 9Be are analyzed in the strong coupling limit by the coupled channel method. A good account of the ground-state (K = 32?) band is obtained, in agreement with the electromagnetic properties of this band. Data for three states of the K = 12+ band are analyzed, yielding much larger isoscalar dipole scattering amplitudes for the 32+ state than are obtained by electron scattering for electric dipole transitions.  相似文献   

6.
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 π+π? 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   

7.
Time-of-flight techniques were used to measure the analyzing power for the scattering of neutrons from 9Be at energies from 9 to 17 MeV. Because of the high nuclear density of beryllium, particular attention was paid to finite-geometry and multiple-scattering effects. For representing the data, an unusual method of Legendre-coefficient analysis was used to establish the smooth energy dependence of both the cross section σ(θ) and the analyzing power Ay(θ). Spherical optical-model calculations were able to describe the σ(θ) and Ay(θ) data simultaneously, but only after the introduction of an imaginary spin-orbit potential Ws.o.(r). The geometry of the Ws.o.(r) term was found to be the same as that of the surface-peaked imaginary central potential. Coupledchannels calculations using a quadrupole-deformed rotational model built on the 32? ground state were able to describe inelastic scattering to the 52? and 72? excited states, but also required a Ws.o.r potential.  相似文献   

8.
The cross section, vector analyzing power, and proton polarization have been measured for the ln = 0 reaction 116Sn(d, p)117Sn(g.s.) at 8.22 MeV. In addition, cross section and analyzing power data have been obtained at 8.22 MeV for 116Sn(d, d)116Sn and for 116Sn(d, p)117Sn leading to excited states of 117Sn at 0.159, 0.317, 1.020, 1.179, 1.308 and 1.497 MeV. The cross section and analyzing power for 117Sn(p,p)Sn and for 117Sn(p, d)116Sn leading to the 1.294 MeV state of 116Sn have also been measured at 12.91 MeV. The data for 116Sn(d, p)117Sn(g.s.) have been used to separate the contributions to the analyzing power arising from spin-dependent forces in the proton and deuteron channels. A similar analysis is presented for an ln = 0 90Zr(d, p)91Zr transition at 11 MeV. Optical-model analyses have been performed for the elastic scattering data. The reaction data have been compared with distorted-wave calculations in order to investigate the validity of various deuteron potentials, as well as to extract spectroscopic information.  相似文献   

9.
An investigation of the γ-decay of the 1g92 analogue state in 59Cu has been performed using the 58Ni(p, γ)59Cu reaction. The (p, γ) excitation function has been taken in the range Ep = 3450–3650 keV. The decay schemes of the (p, γ) resonances at Ep = 3483, 3532 and 3547 keV, measured with Ge(Li) detectors, lead to eight new levels in 59Cu with excitation energies between 1.8 and 4.7 MeV and to spin assignments of several states. The spins of the first two resonances are found to be (12, 32) and (52). The spin of the Ep = 3547 keV resonan is, from angular distributions, uniquely determined to be Jπ = 92+ and this state is found to be the unfragmented analogue state of the E1 = 3.062 MeV, Jπ = 92+ parent state in 59Ni. The measured complete decay scheme of this resonance shows that its isovector M1 decay is in disagreement with all existing theoretical predictions.  相似文献   

10.
Excitation functions of the capture reaction 12C(p, γ0)13N have been obtained at θγ = 0° and 90° and Ep = 150–2500 keV. The results can be explained if a direct radiative capture process, E1(s and d → p), to the ground state in 13N is included in the analysis in addition to the two well-known resonances in this beam energy range [Ep = 457(12+) and 1699 (32?) keV]. The direct capture component is enhanced through interference effects with the two resonance amplitudes. From the observed direct capture cross section, a spectroscopic factor of C2S(l = 1) = 0.49 ± 0.15 has been deduced for the 12? ground state in 13N. Excitation functions for the reaction 12C(p,γ1p1)12C have been obtained at θγ = 0° and 90° and Ep = 610–2700 keV. Away from the 1699 keV resonance the capture γ-ray yield is dominated by the direct capture process E1 (p → s) to the 2366 (12+) keV unbound state. Above Ep = 1 MeV, the observed excitation functions are well reproduced by the direct capture theory to unbound states (bremsstrahlung theory). Below Ep = 1 MeV, i.e., Ep → 457 keV, the theory diverges in contrast to observation. This discrepancy is well known in bremsstrahlung theory as the “infrared problem”. From the observed direct capture cross sections at Ep ? 1 MeV, a spectroscopic factor of C2S(l = 0) = 1.02 ± 0.15 has been found for the 2366 (12+) keV unbound state. A search for direct capture transitions to the 3512 (32?)and 3547 (52+) keV unbound states resulted in upper limits of C2S(l = 1) ≦ 0.5 and C2S(l = 2) ? 1.0, respectively. The results are compared with available stripping data as well as shell-model calculations. The astrophysical aspect of the 12C(p, γ0)13N reaction also is discussed.  相似文献   

11.
Differential cross sections for the 38Ar(α, γ0)42Ca, 40Ar(α, γ0, 1)44Ca and48Ti(α, γ0, 1)52Cr reactions were measured at 90° to the beam direction in 50 or 100 keV steps over the bombarding energy ranges 6.0–15.0 MeV, 5.5–11.1 MeV and 6.0–12.0 MeV respectively. Gamma-ray angular distributions were measured at forty bombarding energies. These show that the (α, γ0) reaction proceeds through 1? levels and to a lesser extent 2+ levels, whereas the (α, γ1) reaction most probably proceeds through 1? and 3? levels. It is deduced that 〈Γ〉/〈D〉 ≦ 1 for the 40Ar(α, γ)44Ca. reaction whereas the fine structure observed in the 48Ti(α, γ)52Cr reaction is probably due to fluctuations. From a comparison with other data it is shown that the (α, γ) reaction is most probably statistical in nature. Using Hauser-Feshbach theory it is deduced that the 36Ar(α, γ)40Ca. reaction is inhibited by isospin selection rules and an estimate is made of isospin mixing in the 40Ca giant dipole resonance. The 38Ar(α, γ)242Ca and40Ar(α, γ)44Ca data are considered with respect to theories of isosopin splitting of the giant dipole resonance.  相似文献   

12.
Angular distributions, a 0° excitation function and Doppler-broadened γ-ray profiles for the reaction 15N(p, α1γ), and angular distributions for the 15N(p, α0) reaction, have been measured for proton energies from about 900 to 1250 keV. These data, together with analysing powers from the 15N(p, α0) reaction, have been satisfactorily fitted by means of R-matrix theory in terms of the known levels of 16O in the 13 MeV region together with background contributions.  相似文献   

13.
The reaction 12C(7Li, t)16O has been studied at E(7Li) = 34 MeV with the LASL tandem accelerator and QDDD magnetic spectrometer. Angular distributions to levels with Ex < 11 MeV have been obtained from 0° to 90°, including 0°. The results have been analyzed with finite-range distorted-wave Born approximation theory. The α-particle spectroscopic factors and reduced widths obtained are compared with those calculated with group theory (SU(3)) and other models. The analysis of data for the 7.1 and 9.6 MeV Jπ = 1? levels, which are of great importance in stellar helium buring, yields a ratio, R, of dimensionless reduced α-widths θ2a(7.1 MeV)θ2a(9.6 MeV) = 0.35b ± 0.13. The observed line width of the 9.6 MeV level (Γc.m. = 390 ± 60 keV) is less than the accepted value (Γc.m. = 510 ± 60 keV) and implies θ2a(9.6 MeV) ≈ 0.6. These results as well as data for the 6.92 MeV Jπ = 2+ and 10.35 MeV Jπ = 4+ “α-cluster” states indicate 0.09 < θ2a(7.1 MeV) < 0.33 with a mean value θ2a(7.1 MeV) = 0.14 ± 0.04. The implication for stellar helium burning is discussed.  相似文献   

14.
Analyzing powers of the continuum spectra were measured for 65 MeV protons from 12C, 28Si, 45Sc, 58Ni, 93Nb, 165Ho, 166Er, 209Bi(p, p#prime;X) and (p, dX) reactions and from 93Nb, 209Bi(p, αX) reactions. The analyzing powers of the continuum spectra were found to be small at forward angles where the pre-equilibrium process is important. However they do not show a systematic tendency. This feature indicates the importance of the spin-dependent interaction as well as nuclear structure effects. On the other hand, the analyzing powers were very large and positive at backward angles where the shape of the energy spectra resembles that of an evaporation spectrum. The maximum values of the analyzing power in the backward hemisphere depend on the target mass for the A < 45 mass region and they are as large as 15%, 20% and 35% for 93Nb(p, pX), (p, dX), (p, αX) reactions at EX = 20 MeV, respectively. These large values are mainly due to the entrance channel effect. There is no appreciable even-odd mass effect on the analyzing power for medium-mass nuclei. These features were unexpected from the conventional pre-equilibrium reaction models.  相似文献   

15.
High-spin states of 39K and 42Ca have been investigated with the 28Si(16O, αpγ)39K and 28Si(16O, 2pγ)42Ca reactions at a beam energy of 45 MeV. Gamma-gamma coincidence, γ-ray angular distribution and linear polarization measurements were performed with a Ge(Li)-NaI(Tl) Compton suppression spectrometer and a three-crystal Ge(Li) Compton polarimeter. High-spin states of 39K at Ex = 7.14,7.78and8.03 and of 42Ca at Ex = 7.75MeV are established. Unambiguous spin-parity assignments of Jπ = 112?, 132?, 152+, 152?, 172+and192? to the 39K levels at Ex = 5.35, 5.72, 6.48, 7.14, 7.78 and 8.03 MeV and of 6?, 7?, 8?, 9? and(8, 10)? to the 42Ca levels at Ex = 5.49, 6.15, 6.41, 6.55 and 7.37 MeV, respectively, have been obtained. Further spin-parity restrictions, lifetime limits, excitation energies, branching ratios and multipole mixing ratios are reported. Discrepancies with previous Jπ assignments are discussed in detail.  相似文献   

16.
High-spin states of 38Ar have been studied with the 35Cl(α, pγ)38Ar reaction at Eα = 18 MeV and with the 24Mg(16O, 2pγ)38Ar reaction at E(16O) = 38 and 45 MeV. The 38Ar level scheme is obtained with the former reaction from a proton-γ coincidence measurement. Gamma-gamma coincidence, γ-ray angular distribution and linear polarization experiments have been performed with a Ge(Li)-Na(Tl) Compton suppression spectrometer and a three-crystal Ge(Li) Compton polarimeter. Unambiguous spin-parity assignments of Jπ = 7?, 7+, 8 +, 7?, 9?and 11?to the 38Ar levels at Ex = 7.51, 8.08, 8.57, 8.97, 10.17 and 11.61 MeV, respectively, are obtained. The 8.57 MeV, 8+ level has a mean life below 0.8 ps. Excitation energies, branching ratios, multipole mixing ratios and transition strengths are reported. The experimental results are compared with shell-model calculations.  相似文献   

17.
Total cross sections for the 16O(p, α0)13N reaction have been measured by observation of the positron decay of the residual 13N nuclei. These cross sections, covering the c.m. energy range 5.4 ≦ E ≦ 9.9 MeV, allow determination of reaction rates of astrophysical interest at temperatures in the neighborhood of 4 × 109°K.  相似文献   

18.
Yrast states of 41K and 41Ca have been investigated with the 26Mg(18O, p2nγ)41K and 26Mg(18O, 3nγ)41Ca reactions at a beam energy of 34 MeV. Gamma-gamma coincidence, γ-ray angular distribution and linear polarization measurements were performed with a Ge(Li)-NaI(Tl) Compton suppression spectrometer and a three-crystal Ge(Li) Compton polarimeter. Unambiguous spin-parity assignments of Jπ = 72+, 112+, 112?, 132+, 152? and 192? to the 41K levels at Ex = 1.68, 2.53, 2.76, 2.77, 4.27 and 4.98 MeV and of 92+, 112+and152+to the 41Ca levels at Ex = 3.20, 3.37 and 3.83 MeV, respectively, have been obtained. Excitation energies, branching ratios, multipole mixing ratios and transition strengths are reported. The main features of the 41K and 41Ca level and decay schemes are reproduced in a 2p-1h and 3p-2h shell-model calculation.  相似文献   

19.
E. Hagn  E. Zech  G. Eska 《Nuclear Physics A》1981,361(2):355-367
The hyperfine splitting frequencies NBH.F./h of 2.7 h 93Tc (Jπ = 92+), 4.9 h 94Tc (Jπ = 7+) and 20 h 95Tc (Jπ = 92+) as dilute impurities in Fe have been measured with NMR on oriented nuclei as 336.36(5) MHz, 175.11(1) MHz and 315.97(2) MHz, respectively. From the resonance shifts with an external magnetic field B0 the hyperfine field of TcFe has been determined as -317(5) kG. Taking this into account the nuclear g-factors are deduced as g(93Tc) = 1.392(22), g(94Tc) = 0.725(11) and g(95Tc) = 1.308(21).  相似文献   

20.
Resonances in the reaction 56Fe(p, γ)57Co have been surveyed over the energy range 1.2 ? Ep ? 1.5 MeV wherein the analogues of the ground state (Jπ = 12?, 0.014 MeV state (Jπ = 32?) and 0.136 MeV state (Jπ = 52?) of 57Fe are expected to occur. Gamma-ray angular distributions have been used to establish resonance and bound-state spins, and decay schemes have been determined. The analogue resonances appear to be severely fragmented, however the density of resonances of a given spin correlates quite well with (3He, d) results and with the expected analogue-state positions.  相似文献   

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