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1.
The lowest four levels of 17O have been observed as resonances in the 13C(α, n)16O reaction. Excitation energies and widths obtained for these levels are 11.076 ± 0.005 MeV, Γc.m. = 5.0 ± 1.1 keV; 12.458 ± 0.005 MeV, Γc.m. = 8 ± 2 keV; 12.944 ± 0.006 MeV, Γc.m. = 6 ± 2 keV; 12.993 ± 0.006 MeV, Γc.m. < 3 keV. The total and partial decay widths for the lowest level are much larger than those of the analogue level in 17F, implying significant isotensor components in the admixtures. 相似文献
2.
M.A. Van Driel H.H. Eggenhuisen J.A.J. Hermans D. Bucurescu H.A. Van Rinsvelt G.A.P. Engelbertink 《Nuclear Physics A》1974,226(2):326-346
The τ = 22 μs isomeric level of 38K at an excitation energy of 3458.0 ± 0.2keVf is strongly populated in the 24Mg(16O, pnγ)38K reaction. Delayed γ-rays are studied with Ge(Li), Si(Li), and NaI detectors. Accurate excitation energies, branching ratios and lifetimes of levels involved in the decay of the isomeric state are determined. The isomeric level predominantly decays by a dipole transition of 38.03±0.03 keV with a total conversion coefficient of αT = 0.42 ± 0.15. Mean lives of 38K levels are measured with the recoil-distance method. The results are τm = 10.1 ± 0.9 ps, 1.41 ± 0.14 ns and 101 ± 15 ps for the levels at excitation energies of 0.46, 2.65 and 3.42 MeV, respectively. It is suggested that the (1f)2 structure of a low-lying Jπ = 7+ state in combination with the selection rules for γ-decay in a self-conjugate nucleus is responsible for the isomerism. 相似文献
3.
Levels in 42Ti up to 4 MeV have been investigated using the 40Ca(3He, n)42Ti reaction and a neutron time-of-flight method. Using the DSA method, lifetimes of 750±300, > 200, 350±250, > 2000 and < 250 fs have been measured for levels at Ex = 1.56, 1.85, 2.40, 2.68 and 3.74 MeV respectively. The level at Ex = 3043.0±1.5 keV is tentatively identified as the 6+ member of the configuration, and its mean life has been measured as 26±5 ns by a direct timing method. Using isospin formalism, transition strengths are compared with theoretical and experimental values for 42Ca and 42Sc. 相似文献
4.
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
5.
R. Lutter O. Häusser D.J. Donahue R.L. Hershberger F. Riess H. Bohn T. Faestermann F.v. Feilitzsch K.E.G. Löbner 《Nuclear Physics A》1974,229(2):230-240
The g-factor of the 480 ns, 9? isomer at 2.237 MeV in 200Pb was measured by the time-differential perturbed angular distribution method. The result, g = ?0.0285±0.0011 confirms the rather pure quasiparticle structure of this state. Half-lives of 480±20 ns, 43±3 ns and 42±4 ns have been measured for the 2237 keV 9?, 2154 keV 7? states in 200Pb and the 2208 keV state in 202Pb, respectively; E2 transitions and g-factors of negative-parity states in even, neutron-deficient Pb isotopes are discussed. 相似文献
6.
K.R. Cordell S.T. Thornton L.C. Dennis P.G. Lookadoo T.C. Schweizer J.L.C. Ford J.Gomez Del Campo D. Shapira 《Nuclear Physics A》1979,323(1):147-160
Excitation functions were measured for states of 21Ne populated by the reaction over the bombarding energy range Elab = 18.2–32.0 MeV (18.4–27.0 MeV) at θlab = 7°(25°) in in 200 keV steps, and average coherence widths of states and the moment of inertia of the compound nucleus 25Mg were obtained from these excitation functions. A statistical analysis of these data was performed. Angular distributions for states in 21Ne to 10 MeV in excitation energy were measured at θlab = 7°, 18°, 28° and 43° at bombarding energies from 29.0 to 31.0 MeV in 400 keV steps. These data along with Hauser-Feshbach predictions allow us to suggest spins for some states as well as to suggest possible candidates for rotational bands in 21Ne. 相似文献
7.
The differential cross section and polarization for neutrons scattered from 10B have been measured at En = 2.63 MeV (Ex = 13.85 MeV). The results of this experiment and other available neutron scattering data in the range 1 < En < 4 MeV are interpreted through a single-level R-matrix calculation over the region 12 < Ex < 15 MeV. Based on this analysis the most probable Jπ assignment for the 14.0 MeV level in 11B is . The anomaly near Ex = 13.1 MeV can only be explained in terms of two overlapping levels having assignments of (, )? and (, , )+. 相似文献
8.
C.P. Swann 《Nuclear Physics A》1973,201(3):534-540
The Doppler-broadened 7.117 MeV line from the 19F(p, αγ)16O reaction has been used to resonantly excite levels in 208Pb at 7071±2 and 7091±2 keV, in 207Pb at 7186±5 and 7206±5 keV and in 209Bi at 7179±5 and 7202±5 keV. On the basis of angular distribution measurements the 7071 and 7091 keV levels of 208Pb are assigned spins of 1 and assuming 100% ground state branching the widths are calculated to be 31±3 and 17±2 eV respectively. It is suggested that the states in 207Pb and 209Bi arise from the weak coupling of a neutron hole and an proton respectively to one or the other of the 208Pb levels. The widths obtained in terms of gΓo2/Γ are 15±4 and 25±5 eV for the 7186 and 7206 keV levels of 207Pb and 24±5 and 30±5 for the levels of 209Bi respectively. These values are consistent with the weak-coupling suggestion. 相似文献
9.
Levels of the N = 81 nucleus 145Gd have been investigated by in-beam γ-ray and conversion electron spectroscopy with the 144Sm(3He, 2n) reaction. Fourteen new low- and medium-spin states between 1.0 and 2.4 MeV excitation, the known yrast levels up to spin , five other high-spin non-yrast states and a new 20.4 ns isomer at 2200.2 keV in 145Gd have been observed. The isomer decays via a fast 927.3 keV E3 transition with B(E3) = 48 ± 7 W.u. Another weaker decay branch is a mixed, strongly hindered E1 + M2 + E3 transition to the state. We propose an octupole main configuration for the isomer, analogous to the 997 keV isomer in 147Gd. The levels of 145Gd are discussed on the basis of the spherical shell model. 相似文献
10.
Energy levels of 85Rb and 87Rb have been studied via de-excitation γ-rays following Coulomb excitation with 35Cl ions. In addition to the known negative-parity states at 151.2 keV and 868.2 keV in 85Rb, two states at 281.0 keV and 731.8 keV have been found with fourγ-ray transitions of 129.8, 281.0, 450.8 and 731.8 keV. Only one Coulomb excited state at 402.6 keV in 87Rb has been observed. The B(E2↑) values (in units e2 · b2) have been determined as 0.0035±0.0004 (151.2 keV), 0.0016±0.0002 (281.0 keV), 0.0101 ±0.0010 (731.8 keV), and 0.036±0.004 (868.2 keV) for the states in 85Rb, and as 0.0054±0.0006 (402.6 keV) for the state in 87Rb. The mean lifetimes of the 731.8 keV and 868.2 keV states have been measured by the Doppler shift attenuation method as 6.4±0.7 psec and 4.2±0.5 psec respectively. Angular distribution measurements allow unique spin and parity assignments of and to the 281.0 keV and 731.8 keV levels respectively. The spin and parity of the 868.2 keV level has been restricted to or . 相似文献
11.
Angular correlations have been measured between γ-rays from the 2 → 2 → 0 cascades in 106,112,114Cd and the beam of 11.0 MeV α particles effecting Coulomb excitation. Multipole admixtures for the 2 → 2 transitions, as deduced from these correlations, when combined with earlier results establish their B(E2) and B(M1) values. For the transitions from the 1312 and 1208 keV states in 112,114Cd the B(E2) values in single-particle units are 18±4 and 24±7. These values are typical for transitions from “two-quadrupole-phonon” states in this mass region whereas that of the 1718 keV transition in 106Cd has the smaller value of 7.0±2.3. The B(E2) values of the 2 → 2 transitions in 112,114Cd from the 1468 and 1363 keV states are < 0.3 single-particle units. The B(M1) values of all five transitions are ≈ 10?2. 相似文献
12.
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
13.
Nanosecond lifetimes of several states in 147Nd have been studied using the reaction 146Nd(d, pγ)147Nd with 10 MeV deuterons. The following lifetimes were observed: the level at 49.9 keV, 2.5±0.5 ns; the level at 127.9 keV, ≦ 0.8 ns; the level at 190.3 keV, 1.1±0.3 ns and the level at 214.6 keV, 5.8±0.8 ns. The wave functions of the states were constructed using an axial particle-plus-rotor model. The free parameters used are compared to the systematics observed in the neighbouring heavier N = 87 isotones as well as in the N = 89 and 91 isotones. Transition rates within the and based excitations, separately, are reasonably well reproduced, but the connecting transitions indicate too strong a mixing of the shells in the calculation. 相似文献
14.
The inelastic α-scattering reaction at Eα = 120 MeV with an energy resolution of 90–150 keV has been used to investigate isoscalar strength distributions in 24, 26Mg, 28Si and 40Ca. For 24, 26Mg and 28Si the E2 strength between Ex = 14 and 27 MeV is strongly fragmented. In 40Ca the E2 strength is mainly concentrated near MeV, although here the onset of fragmentation can be observed. The sum rule strength for the different multipolarities was obtained by applying for each nucleus an L-dependent normalization procedure. In this way we observed in total in 24, 26Mg, 28Si and 40Ca for excitation energies up to 27 MeV an amount of (61+8?6), (50+9?8), (38+8?6) and (94 ± 14)%, respectively, of the isoscalar E2 energy weighted sum rule (EWSR) of which (36+7?5), (28+8?7), (24+7?5) and (74 ± 12)% was found between Ex = 14 and 27 MeV. In addition isoscalar E0, E3 and E4 strength was observed in this excitation energy region. A detailed comparison has been made between the isoscalar quadrupole strength distribution observed in the 24, 26Mg(α, α') reaction and the E2 strength excitation function obtained from radiative α-capture measurements. In the low excitation energy region coupled channel effects have been observed, especially for the excitation of the 3+ states. Moreover, a considerable percentage of the 1?ω isoscalar dipole and octupole strength has been observed for excitations below 14 MeV. 相似文献
15.
Five rotational bands in 172Hf have been observed to high spin following the 160Gd(16O, 4n)172Hf reaction, using γ-γ coincidence techniques. The ground-state band is extended to spin 20+ without backbending, in contrast to the neighbouring even-even isotones. The most strongly populated side-band, consisting of separated odd-spin and even-spin sequences, appears to result from the partial decoupling of an i neutron. Three other bands are identified with the following band-heads: an 8? state at 2006 keV with 163 ns half-life; a 6+ state at 1685 keV with a half-life < 16 ns; and a level at 1857 keV with spin 4, 5, 6 or 7 and a half-life < 16 ns. The differences between the bands are discussed in terms of the influence of Coriolis forces and the two-quasiparticle level structure. 相似文献
16.
The de-excitation of the 215 keV and 324 keV levels in97Tc, as observed in 97Ru decay, was studied by means of internal conversion electron spectroscopy and the delayed electron-electron coincidence technique. From L-subshell intensity ratios, the E2 content in the 108 and 215 keV transitions were found to be (65 ± 12)% and (7 ± 4)%, respectively. The obtained level mean-lives were 0.75 ± 0.09 ns for the 324 keV level and 74 ± 15 ps for the 215 keV level. 相似文献
17.
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
18.
The 20Ne(p, γ)21Na capture reaction has been studied in the energy range Ep = 0.37–2.10 MeV. Direct-capture transitions to the states have been found with spectroscopic factors of C2S(1d) = 0.77±0.13 and C2S(2s) = 0.90±0.12, respectively. The high-energy tail of the 2425 keV state, bound by 7 keV against proton decay, has also been observed in the above energy range as a subthreshold resonance. The excitation function for this tail is consistent with a single-level Breit-Wigner shape for a γ-width of Γγ = 0.31±0.07 eV at Ex = 2425 keV. The extrapolation of these data to stellar energies gives an astrophysical S-factor of S(0) = 3500 keV · b. Two new resonances at Ep = 384±5 and 417± 5 keV have been observed with strengths of ωγ = 0.11±0.02 and 0.06±0.01 meV, corresponding to the known states at and 2829 keV (presumably ), respectively. For the known Ep = 1830 keV resonance, a strength of ωγ = 1.0± 0.3 eV and a total width of Γ = 180± 15 keV were found. Branching ratios as well as transition strengths have been obtained for these three states. The Q-value for the 20Ne(p, γ)21Na reaction (Q = 2432.3 ± 0.5 keV) as well as excitation energies for many low-lying states in 21Na have been measured. No evidence was found for the existence of the state reported at Ex = 4308±4 keV.In the case of 22Ne(p, γ)23Na, direct-capture transitions to six final bound states have been observed revealing sizeable spectroscopic factors for these states. The astrophysical S-factor extrapolated from these data to stellar energies, is S(0) = 67 ± 12 keV · b.The astrophysical as well as the nuclear structure aspects of the present results are discussed. 相似文献
19.
Excitation functions for 16O+p reactions have been measured with high energy resolution in the region of the first, second and seventh resonances in 17F at extreme backward angles. The observed resonance shapes have been analyzed with a single-level resonance formula taking the off-resonance spin-flip amplitude into account. The resonance parameters of the 17F first state studied with special emphasis are Ex = 11193.3 ± 2.3 keV, Γ = 200 ± 40 eV and Γp0 = 19 ± 3 eV. This result and other results are compared with previous studies and theoretical predictions. The comparison with data of the mirror nucleus 17O is discussed with respect to the observed charge asymmetry of the isospin-forbidden particle decay widths. 相似文献
20.
C. Dionisi R. Armenteros J. Diaz Ph. Gavillet J.B. Gay A. Gurtu R.J. Hemingway M. Mazzucato P. Trepagnier R. Blokzijl G.G.G. Massaro B. Jongejans J. Engelen J.J. Timmermans R.T. Van De Walle B. Foster P.R. Lamb W.L. McDowell 《Physics letters. [Part B]》1978,78(1):154-157
Evidence is presented for an I = 1 enhancement observed in the reactions K?p→Λ(Σ)K01K±π? at inciden momentum. The mass and width of the proposed new Y1 are, respectively, (1553 ± 7) MeV) and (80 ± 30) MeV. A decay branching ratio is also obtained. 相似文献