共查询到20条相似文献,搜索用时 31 毫秒
1.
J.S. Forster T.K. Alexander G.C. Ball W.G. Davies I.V. Mitchell K.B. Winterbon 《Nuclear Physics A》1979,313(3):397-424
Accurate lifetimes have been measured for low-lying levels in 22Ne, 28Si and 31P by bombarding 4He implanted targets with beams of 19F and 28Si ions. Mean lifetimes determined by fitting Doppler-broadened γ-ray lineshapes were ). The lifetime values for the 3.357 MeV level in 22Ne and the 2.234 MeV level in 31P are used to calibrate low velocity DSAM lifetime data for these two levels and to obtain scaling factors to theoretical electronic stopping powers for Ne and P ions. 相似文献
2.
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
3.
4.
Transient field precession measurements have been performed on the first excited Jπ = 2+ states of 28Si and 30Si with the IMPAC technique on recoil in magnetized iron. The results were analyzed with empirically adjusted Lindhard-Winther predictions. This yields g-factors of , respectively. In the present cases the influence of static hyperfine fields is negligible due to the very short mean lives for 28Si and 30Si of 0.68 and 0.35 ps, respectively. The results are compared with theoretical calculations. Previous results for 26Mg(21+) were reanalyzed with the more recent lifetime of τm = 0.72 ± 0.03 ps. The value of the g-factor becomes g = +0.82 ± 0.16. 相似文献
5.
The (n, 2n) cross sections at neutron energies between 14.9 and 17.0 MeV have been measured for 85Rb, 87Rb and 144Sm by the mixed-powder method and γ-ray detection by a Ge(Li) spectrometer. Using the 27Al(n, α)24Na reaction for monitoring, the measured cross sections were (in mb): . The measured values are compared with the statistical model calculations of Pearlstein. 相似文献
6.
R.A. McCulloch N.M. Clarke R.J. Griffiths J.S. Hanspal S. Roman J.M. Barnwell 《Nuclear Physics A》1984,431(2):344-366
Distributions of cross sections and analysing powers have been measured over the range ~ 14°–100° c.m. for the 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 state, and a level near 9.5 MeV in 31P as a possible 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
7.
Results from a CCBA analysis of the 28Si(d, 3He)27Al reaction are reported. The transfers are assumed to occur between dominant components of (λμ) symmetry (0, 12) and (2, 10) in the initial and final nuclear eigenstates respectively. The results show that cross sections to four of the six levels observed below 3 MeV can be fairly well reproduced within a pure K(J) band framework. However, consistent with electromagnetic results, all six levels can be fit if the K(J) band purity of the analysis, SU(3) model. states and state is abandoned. 相似文献
8.
9.
The α-decay properties of very short-lived N = 128 isotones, 216Ra, 217Ac and 218Th, were investigated by the pulsed-beam method. Alpha emitters of interest were produced in the bombardment of 208Pb or 209Bi with 65–96 MeV 12C or 14N ions and α-decays were measured between natural beam bursts of the cyclotron. The results obtained are Eα = 9.349±0.008 MeVand and and . The experimental reduced α-widths of N = 128 isotones from 212Po to 218Th are shown to agree well with the simple shell model calculation. 相似文献
10.
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
11.
The reaction 48Ti(t, d)49Ti leading to the ground and first excited states of 49Ti has been studied at triton energies of 2.75 and 3.0 MeV. The cross section to the ground state of 49Ti has been analysed using the DWBA with a previously determined bound-state well geometry to obtain a value for the (t, d) normalization factor of D2 = (3.29 ± 0.40) × 104 MeV2 · fm3. This value is in agreement with that obtained from a comparison of the (d, t) reaction with heavy-ion single-neutron transfer reactions. Using this value of the normalization factor the rms radius of the component in the first excited state of 49Ti is found to be 4.42 ± 0.07 fm (point neutron), corresponding to the use of a local bound-state potential well. 相似文献
12.
The 20Ne(3He, n) reaction leading to the ground state of 22Mg has been investigated in the 3He+ energy range of 2.6 to 4.0 MeV. Angular distributions were determined with a neutron time-of-flight spectrometer at average incident energies (lab) of 3.27, 3.69, and 4.01 MeV between 0° and 120° (lab). Excitation functions for the energy region were measured at 0° and 80° (lab). The observed differential cross sections are explained by coherent contributions from direct interaction and compound-nucleus formation. A spectroscopic factor was extracted for the DWBA calculation from the absolute cross-section measurements and found to be . Resonances in the compound-nucleus formation were found at 3.00 and 3.33 MeV (c.m.) with widths of 0.28 and 0.21 MeV and spins of , respectively. 相似文献
13.
Levels in 51Cr, 53Cr, 53Mn and 53Fe were excited via (α, n) or (α, p) reactions. Using the recoil-distance method, mean-lives (in ps) have been obtained for excited states (keV) in the residual nuclei: . Reduced transition probabilities calculated from these values are compared with the available theoretical values. 相似文献
14.
E. Arai M. Futakuchi H. Kamada J. Komaki T. Matsuzaki M. Ogawa Y. Oguri 《Nuclear Physics A》1982,378(2):259-272
Using a proton beam with an overall resolution of 300–400 eV (FWHM) spins, parities and partial widths were determined for all resonances observed (99 s-wave, 42 p-wave, 106 d-wave and one g-wave resonances). Differential cross sections for proton elastic scattering from 56Fe were measured at proton energies between 3.1 and 4.2 MeV. Spectroscopic factors and Coulomb displacement energies were extracted for the fragmented analogue resonances which correspond to the , and states in 57Fe. A value of the s-wave proton strength function was deduced. 相似文献
15.
J. Arvieux M. Buenerd A.J. Cole P. De Saintignon G. Perrin D.J. Horen 《Nuclear Physics A》1975,247(2):238-250
Spectra of 48Ti, 56Fe, 59Co and 60Ni have been investigated for excitation energies of 10–20 MeV by inelastic scattering of 80 MeV 3He particles. Broad peaks with excitation energies of about and FWHM of 6 MeV have been observed. Much narrower satellite peaks occur at excitation energies about . The angular distributions of the sum of these peaks were compared to extended optical model DWBA calculations which confirm the predominant L = 2 character of the GR. A tentative assignment of L = 2 or 4 was made for the 13.5 MeV satellite peak in 56Fe. We see no definite evidence for the presence of an L = 1 GR component. 相似文献
16.
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
17.
H.H. Eggenhuisen L.P. Ekström G.A.P. Engelbertink H.J.M. Aarts J.A.J. Hermans 《Nuclear Physics A》1977,285(1):167-188
Yrast levels in 40K and 40Ar have been investigated with the 26Mg(16O, pnγ)40K and 26Mg(16O, 2pγ)40Ar reactions at a beam energy of 34 MeV. Gamma-ray angular distribution and γ-γ coincidence measurements have been performed with a high-resolution large volume Ge(Li)-NaI(Tl) Compton-suppression spectrometer. Gamma-ray linear polarizations have been measured with a three-crystal Ge(Li) Compton polarimeter. The 40K decay scheme involves new high-spin levels at Etx = 4365.6±0.3, 4875.6±0.4 and 6227.0±0.5 keV with lifetime limits of < 1, < 1 and < 2ps, respectively. Unambiguous spin-parity assignments of to the 40K levels at Ex = 0.89, 2.88, 4.37, 4.88 and 6.23 and of levels at Ex = 2.89 and 3.46 MeV, respectively, have been obtained. Branching ratios and multipole mixing ratios are reported. 相似文献
18.
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 . The 14.40 MeV state is a strongly isospin-mixed analog of the 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 states and the lowest three states are compared with the predictions of DWBA utilizing shell-model form factors. It is concluded that the strength is more strongly fragmented than is implied by the calculations of Teeters and Kurath. 相似文献
19.
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
20.
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