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1.
The reaction 12C(7Li, t)16O has been studied at 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 . 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
2.
E.H.Du Marchie Van Voorthuysen M.J.A. Devoigt N. Blasi J.F.W. Jansen 《Nuclear Physics A》1981,355(1):93-114
The level schemes of 98, 99Ru were studied with the reactions 98Mo(α, 3nγ) and 98Mo(α, 4nγ) at Eα = 35 to 55 MeV, using a large variety of in-beam γ-ray detection techniques and conversion-electron measurements. A search for the 3? state was carried out with the reaction 98Ru(p, p′). The ground-state band of 98Ru was excited up to Jπ = (12)+ and a negative-parity band up to (15)?. New levels in 98Ru were found at Ex = 2285 (Jπ = 4+), 2435 (Jπ = (3?, 4+)), 2671, 3540, 4224, 4847, 4915 (Jπ = (12)+), 4989 (Jπ = (12+)), 5521 (Jπ = (13)?), 5889, 6591 (Jπ = (15)?), and 7621 keV. New unambiguous spin and parity assignments were made for the levels at Ex = 2014 and 3852 keV, as Jπ = 3+ and 9?, respectively. New levels in 99Ru were found at Ex = 1976, 2021 (), 2393, 2401 (), 2875 (π = (+)), 3037, 3201 (), 3460 (), 3484 (), 3985, 4224 (), and 5359 keV. The 1070 keV, level in 99Ru has a half-life of 2.8 ns. A strongly excited negative-parity band is built on this level. A positive-parity band based on the ground state was excited up to . The level schemes are well reproduced by the interacting boson model in the vibrational limit. 相似文献
3.
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 state and 0.136 MeV state 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
4.
The hyperfine splitting frequencies gμNBH.F./h of 2.7 h 93Tc , 4.9 h 94Tc (Jπ = 7+) and 20 h 95Tc 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 Tc has been determined as -317(5) kG. Taking this into account the nuclear g-factors are deduced as . 相似文献
5.
O. Häusser T.K. Alexander D.L. Disdier A.J. Ferguson A.B. McDonald I.S. Towner 《Nuclear Physics A》1973,216(3):617-628
The α-decay of several unbound levels in 20Ne has been studied by 16O(α, α) elastic and inelastic scattering. A narrow resonance, Γc.m. = 13±4 eV, with Jπ = 5? was found at and is associated with the lowest K = 2? quasirotational band. Several new, narrow resonances were found between Ex = 16.0?18.4 MeV. Reduced α-decay widths have been obtained for the lowest K = 0+, 2? and 0?bands. For states described predominantly by the (8, 2) representation of SU(3) we note a reduction of the reduced widths with increasing spin. Reduced widths of positive parity bands are reviewed. 相似文献
6.
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 and 1699 . 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 ground state in 13N. Excitation functions for the reaction 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 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 , a spectroscopic factor of C2S(l = 0) = 1.02 ± 0.15 has been found for the unbound state. A search for direct capture transitions to the and 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
7.
Gamma-ray angular distributions, nγ angular correlations, γγ coincidences and Doppler-shift attenuations have been measured in the 42Ca(α, nγ)45Ti reaction. In addition to the known positive-parity levels forming the band members are identified in 45Ti. They are the levels at 1565 keV, 1958 keV, 2258 Reduced transition probabilities are obtained for the γ-decays of these levels as well as for those of the band members. The excitation energies and transition probabilities are well reproduced by a rotation-particle-coupling model calculation with deformation parameter β = 0.30–0.35. 相似文献
8.
A. Cunsolo A. Foti G. Immè G. Pappalardo G. Raciti N. Saunier 《Physics letters. [Part B]》1982,112(2):121-123
Deuteron-alpha angular correlations have been measured for the reaction and θdlab=10°. Transitions involving the 11.69 MeV (6+) and the 17.6±0.2 MeV 18O states have been analyzed. Spin and parity are confirmed for the known 11.69 MeV (6+) state and assigned to be 8+ for the 17.6 MeV level. This last is suggested to be the fifth member of the positive-parity 18O rotational band built on the 3.63 MeV (0+) level. 相似文献
9.
H. Nann W.W. Jacobs A.D. Bacher G. Cravens W.P. Jones E.J. Stephenson 《Physics letters. [Part B]》1982,109(3):175-178
Vector analyzing power angular distributions for the reaction have been measured at 80 MeV bombarding energy. They exhibit large differences between the possible transferred total angular momenta J=L+1, J=L and J=L ? 1, thus allowing unique spin determinations of the levels in the residual nucleus 56Co. This has led to new spin assignments for the following high-spin states in . 相似文献
10.
From the angular distributions of γ-rays emitted by oriented 129gTe and 129mTe nuclei implanted in iron by isotope separator, unique spin assignments could be made for the excited states of 129I at 487.4 keV , 696.0 keV , 729.6 keV , 768.9 keV , 1050.4 keV and 1111.8 keV . In addition, E2/M1 amplitude ratios for the following 129I γ-rays (energies are in keV) are derived: δ(459.6) = ?(0.076+0.037?0.148); δ(487.4) = 0.50+0.17?0.10 or δ? = 0.35+0.15?0.09; δ(556.7) = 0.06±0.02 or δ? = ?(0.10±0.02); δ(624.4) = 0.10±0.26 or δ? > 0.4; the 696.0 keV γ-ray is pure E2; δ(729.6) = ?(0.34±0.06) or δ?1 = 0.55±0.05; δ(741.1) = ?(0.27±0.10) or δ?1 = ?(0.43±0.12); δ(817.2) = 0.46±0.04 or δ?1 =0.20±0.03 if ; δ(1022.6) = ?(0.02 ±0.02) or δ?1 = ?(0.23±0.02); ; δ(1111.8) = 0.06±0.05 or δ?1 = ?(0.08±0.05). The anisotropy of the 531.8 keV γ-ray excludes as a possible spin assignment for the 559.6 keV level, so that no level is fed in the decay from 129Te. Anisotropies for the 209, 250.7, 278.4 and 281.1 keV γ-rays are also measured. Comparison of the level scheme is made with theoretical predictions from both the pairing-plus-quadrupole model and the intermediate coupling unified model. 相似文献
11.
C.J. Van Der Poel G.A.P. Engelbertink H.F.R. Arciszewski P.C.N. Crouzen J.W. De Vries E.A.J.M. Offermann E.J. Evers 《Nuclear Physics A》1983,394(3):501-524
High-spin states in 38K are investigated with the 24Mg(16O, pnγ)38K reaction at . A recently developed Compton-suppression spectrometer with 120 msr solid angle and a pulsed beam are employed to study their γ-decay. For the E4 transition from the isomeric level at Ex = 3458 keV to the ground state a branching ratio of (0.15 ± 0.02)% is found. On the basis of angular distribution and polarization measurements, in which the delayed feeding component is eliminated, spin-parity assignments are obtained of Jπ(2646 keV) = (2, 4)?, Jπ(3420 keV) = (4, 6)? and Jπ(3458 keV) = (5, 7)+. Prompt-delayed and prompt γγ coincidence experiments are performed to locate high-spin levels above the isomer. Hitherto unobserved levels of high spin are found at Ex = 5254, 7397, 8693, 8747 and 10980 keV and assignments of Jπ = (9+), (10?), (12?), (11?) and (13?) respectively, are suggested by weak-coupling considerations. The experimental results are compared with a large-scale shell-model calculation performed in a configuration space with a 28Si core and ten active particles distributed over the ( shells. The high-spin states appear to have a rather simple shell-model structure. 相似文献
12.
Lifetimes of low-lying states in 19F were measured using the Doppler-shift attenuation method through the 15N(α, γ)19F reaction. Values of τm = 3700 ± 700 fs (1.35 MeV), 140 ± 15 (1.46), 19 ± 7 (4.00) and 63 ± 19 (4.03) were obtained for the lowest , , and members, respectively, of the rotational band and 5 ± 3 fs (1.55 MeV) and 370 ± 25 (2.78) for the and members of the ground-state band. For the Doppler-shift attenuation analysis correction factors of the nuclear and electronic stopping powers were determined by measuring the Doppler-shift attenuation and γ-ray line shape of the 2.78 → 0.20 MeV transition and range values of 100, 200. 300 and 370 keV 19F nuclei in tantalum. All calculations were done with Monte Carlo methods. The transition strengths are discussed in terms of different theoretical predictions. 相似文献
13.
High spin states of 57Co have been studied via prompt γ-ray spectroscopy in the reactions 48Ti(12C, p2n) and 54Fe(α, p) at 26–48 MeV and 12–24 MeV, respectively. The energies and decay modes of these levels were determined from the analysis of γ-ray singles and γ-γ coincidence spectra, excitation functions, angular distributions and correlations. The relevant lifetimes were measured by the Doppler-shift attenuation method. The new levels established in this work are at 4037, 4814 and 5918 keV with the most probable Jπ assignment of , if and , respectively. The previously known level at 2524 keV was assigned to have . These together with the known (1224 keV) and (1690 keV) levels constitute the yrast states of 57Co. The measured lifetimes of the above six levels are (in order of increasing energies) 0.085±0.030, 0.32±0.10, 0.16±0.06, 0.10?0.07+0.06, 1.5?0.54 and 0.17?0.07+0.08 ps, respectively. Comparisons with some theoretical calculations are presented. 相似文献
14.
Differential cross sections were measured for the reactions 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 . In general, strong coupled-channel effects mainly affecting the distorted waves are observed both in entrance and exit channels. 相似文献
15.
An investigation of the γ-decay of the 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 (, ) and (). The spin of the Ep = 3547 keV resonan is, from angular distributions, uniquely determined to be and this state is found to be the unfragmented analogue state of the , 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
16.
T. Tachikawa N. Kato H. Fujita K. Kimura T. Sugimitsu K. Morita K. Anai T. Inoue H. Inoue Y. Nakajima M.H. Tanaka S. Kubono 《Physics letters. [Part B]》1984,139(4):267-272
The elastic and inelastic scattering of 12C from 19F leading to the and ) states has been studied at . The angular distributions for the transitions are almost in phase with those of the elastic scattering and cannot be reproduced with the DWBA and CC caculation using collective form factors. 相似文献
17.
Levels of 33S for Ex < 5 MeV have been studied with the 30Si(α, nγ)33S reaction at bombarding energies of Eα = 7.5 and 10.2 MeV. Neutron-gamma angular correlation experiments lead to three unambiguous spin and parity assignments: . The measured branching and mixing ratios yield transition strengths for dipole and quadrupole transitions. 相似文献
18.
Fission-fragment mass and kinetic energy distributions and their correlations have been measured for 232U and 233U. The results on these uranium isotopes and 235U are compared. The mass peak/valley ratio of 785 ± 68 for 232U is the highest of the three isotopes. The 〈EK〉(μH) distributions show significant differences. The dip ΔEK at symmetry is , . In the yields for high-kinetic-energy-selected events, the mass 134 dominates for 233U and 235U, but for 232U it is μH≈144, which dominates. This complete reversal of profiles can be understood in terms of fragment shells. 相似文献
19.
M. Deutschmann G. Otter G. Rudolph H. Seyfert H. Wieczorek H. Böttcher W.D. Nowak S. Nowak V.T. Cocconi M.J. Counihan J.D. Hansen G.T. Jones G. Kellner W. Kittel A. Kotanski D.R.O. Morrison D. Sotiriou T.C. Bacon J. Strauss 《Physics letters. [Part B]》1974,49(4):388-392
A parital wave analysis of the (Kππ) system produced in K?p → (K?π?π+)p at 10 and 16 GeV/c has been performed. It is found that in 88% of the cases the Kππ) system is in unnatural spin-parity (JP) states 0?, 1+, 2? …, with contributions from many decay modes, . More than one decay m and JP state are required to describe the Q and L enhancements, suggesting a composite structure of these enhancements. The (Kππ) system is produced dominantly (~95%) by natural parity exchange. Overall, the production mechanism of the (Kππ) system is remarkably similar to that of the 3π system in π?p → (π?π?π+)p, even i detailed spin-parity structure. 相似文献
20.
Simultaneous production of K1o (892) and Δ++(1236) in the reaction K+p→K+π+π−p from 4.3 to 5.0 GeV/c
G. Dehm G. Göbel W. Wittek G. Wolf G. De Jongh S. Tavernier G. Charrière W. Dunwoodie A. Grant Y. Goldschmidt-Clermont V.P. Henri F. Muller J. Quinquard P. Cornet P. Dufour F. Grard R. Windmolders Chumin Fu 《Nuclear Physics B》1974,71(1):52-81
The reaction from a K+d experiment with the CERN 2 m bubble chamber at 4.6 GeV/c is compared with the reaction from a K+p experiment at the same energy. In addition, predictions of an absorption model, a Regge pole model and a quark model for the production and decay characteristics of the reaction are tested with the combined statistics of the K+d experiment and three K+p experiments between 4.3 and 5.0 GeV/c. 相似文献