G.C. Neilson

Pulsed beam lifetime measurements in 64Cu, 59Ni, 65Zn, 45,47,49Ti and 47,49,50,51V

Abstract The lifetimes of several excited states in 64 Cu, 59 Ni, 65 Zn, 45,47,49 Ti and 47,49,50,51 V have been determined using a direct timing technique. Data for 64 Cu were obtained in order to provide reference γ-rays for use in the measurements on the Ti and V isotopes. Several states in 64 Cu were found to provide conveniently fast low-energy γ-ray decays : E ( ρ m ) are; 159 (29.8 ± 5.4), 278 ( 45 Ti 330 (1585 ± 20); 47 Ti 160 (301 ± 8), 1795 ( 49 Ti 1381 ( 47 V 88 (951±52), 146 (786 ± 95), 260 (78 ± 11); 49 V 90 (329 ± 19), 153 (28.71 ± 0.35 ns); 50 V 226( 51 V 320 (266 ± 9), 928 ( 59 Ni 340 (93 +- 10), 465(35 ± 18); 65 Zn 115 (641 ± 13), 207 (216 ± 10), 769 (

Nuclear structure studies of phosphorous isotopes: (II). The 28Si(d, n)29P reaction

Abstract Angular distributions of the neutrons leading to states of 29P up to an excitation of 3.5 MeV were obtained using the 28Si(d, n)29P reaction for deuteron energies of 4 and 5 MeV. The angular distributions for the ground, first and second excited states of 29P were analysed using the distorted wave Born approximation. The experimental spectroscopic factors favour a Nilsson model description for the 29P nucleus. Evidence for spin dependent structure was seen in the angular distributions of neutrons leading to the 1.38 MeV ( J π = 3 2 + ) and 1.96 ( J π = 5 2 + ) MeV states of 29P.

The excited states of 10B

Abstract The reaction 9 Be(d, n) 10 B has been studied by time-of-flight techniques at bombarding energies of 3.0, 3.5 and 5.5 MeV. A total of 16 levels of 10 B was identified up to 7.5 MeV excitation, but no significant evidence was found for reported states at 5.18, 5.58, 6.40 and 6.77 MeV. The DWBA theory was used to interpret the angular distributions for l -values and spectroscopic factors, and plane wave theory was used in cases where the 10 B levels become unbound. The spectroscopic factors were found to depend sensitivity on optical parameter uncertainties and also on whether or not finite-range and non-local effects were included.

A new search for rescattering effects in the 7Li+d → α+α+n reaction

Abstract Rescattering effects in the 7 Li(d, αα)n reaction are re-examined at incident deuteron energies between 1.90 and 2.10 MeV. The previously reported effects attributed to rescattering following the formation of the resonance state at 16.63 MeV in 8 Be are not observed. Conditions affecting the observation of such a rescattering are discussed.

Measurements of neutron angular distributions from the 7Li(p, n)7Be reaction☆

Abstract The absolute zero-degree differential cross sections of the 7 Li(p, n 0 ) 7 Be and the 7 Li(p, n 1 ) 7 Be reactions have been measured with a time-of-flight spectrometer at 0.1 MeV intervals from 2.20 to 5.50 MeV. Angular distributions of neutrons from both reactions were also measured at 0.2 MeV intervals from 2.60 to 5.40 MeV for the n 0 neutron group and from 3.20 to 5.40 MeV for the n 1 group. Absolute differential cross sections were obtained by normalization to the zero-degree measurement. The centre-of-mass distributions were fitted with a Legendre polynomial series. Total cross sections were obtained by integrating the angular distributions. The comparison between present and previous results has revealed some disagreement in the shapes of angular distributions and in the magnitude of total cross sections for the 7 Li(p, n 1 ) 7 Be reaction.

The 40Ca(d,n)41Sc reaction; neutron polarization and angular distribution measurements

Abstract The angular distributions and neutron polarizations have been measured for the reaction 40 Ca(d,n) 41 Sc at a deuteron bombarding energy of 6 MeV. The polarization measurements, from 0° to 120°, were made for neutron groups corresponding to the ground, 1.718 MeV and 2.415 MeV states in 41 Sc. Additional angular distribution measurements were made for neutron groups corresponding to the 2.096, 2.719 and 3.463 MeV states in 41 Sc. Good agreement is found between the observed and DWBA predicted neutron angular distributions. No satisfactory agreement between the experimental and calculated neutron polarizations is found for any reasonable choice of optical parameters.

The 20Ne(d, n)21Na reaction

Abstract The structure of 21 Na has been investigated using the 20 Ne(d, n) 21 Na reaction at E d = 3.92, 5.16 and 6.08 MeV. Differential cross sections have been obtained for neutron groups corresponding to the four bound states of 21 Na. The data are compared with DWBA and Hauser-Feshbach predictions for direct and compound reaction cross sections. Absolute spectroscopic factors are deduced for the 21 Na bound states and are compared with predictions of the Nilsson and shell model descriptions for this nucleus.

The alpha-particle breakup of the 12.71 and 11.83 MeV levels in C12

Abstract The alpha-particle decay of states in C 12 , with special emphasis on those at 11.83 and 12.71 MeV excitation, has been studied using the B 11 (d, n)C 12 reaction. Neutron time-of-flight spectra and semiconductor detector charged-particle spectra were analysed by a two-parameter pulse-height analyser. Angular and energy distributions of the alpha particles from the 12.71 and 11.83 MeV states indicate that these states decay sequentially through Be 8 . The 1 + spin-parity assignment for the 12.71 MeV state is supported by the fact that no transitions to the ground state of Be 8 were observed. Approximately 90% of the transitions from the 11.83 MeV state proceed via Be 8 (2.9 MeV) while the remaining 10% feed the ground state. There is some evidence to indicate that the 10.84 MeV state of C 12 decays exclusively to Be 8 (0). The 3 − assignment for the 9.64 MeV state in C 12 is favoured over 1 − on the basis of the angular distribution of the alpha particles from this state to the Be 8 ground state. This work, together with other reported in the literature, justifies the representation of C 12 as a Be 8 +α two-body cluster from the alpha-particle threshold to 16 MeV excitation. Such a representation is in accordance with the two-body cluster model of Phillips and Tombrello.

Hole states in 55Fe

Abstract A number of low-lying levels in 55 Fe have been described as hole states. The lifetime of the first two hole states has been measured using the direct-timing and Doppler-shift techniques, and the decay scheme of these and neighbouring levels measured. An unsuccessful search was also made for possible decays from a level which has been reported at an excitation of 2818 keV. The experimental information is compared with various calculations.

Energy levels of 45Ti excited in the 45Sc(p, n)45Ti reaction

Abstract The energy levels of 45 Ti excited in the reaction 45 Sc(p, n) 45 Ti were investigated by neutron time-of-flight technique. Levels in 45 Ti at 1.521, 1.800, 1.880 and 2.020 MeV were observed for the first time through this reaction. Angular distributions of the neutron groups to the ground state, 0.040, 0.330, 0.744, 1.226, 1.353 and 1.468 MeV levels were measured at a mean proton energy of 5.330 MeV. The neutron distributions to the ground state, 0.040, 0.330 and 0.744 MeV levels of 45 Ti were compared with the predictions from Hauser-Feshbach statistical model and a spin of 5 2 was assigned to the 0.744 MeV level. Gamma rays from the interaction of protons with scandium were observed using a Ge(Li) detector and γ-rays of 293, 414, 482, 707, 896, 1186, 1226, 1313, 1353, 1468 and 1484 keV were observed to arise from transitions between levels of 45 Ti. The angular distributions of the 293 and 414 keVγ-rays were measured at proton bombarding energies of 3.45 and 3.85 MeV respectively and were found to be isotropic.