K.H. Bray

The 27Al(3He, α)26Al reaction at 10 MeV bombarding energy

Abstract The reaction 27Al(3He, α)26Al has been studied at 10 MeV bombarding energy. Angular distributions were measured for the ground state and the first (0.229 MeV), second (0.418 MeV), third (1.059 MeV), “fourth” (1.760/1.852 MeV) and “sixth” (2.07/2.08) MeV excited states in 26Al. The spectra were recorded at every 5° between 15° and 165°(lab). The direct-interaction contributions to the cross sections were calculated using the distorted wave Born approximation and are compared with the observations. The effects of both a finite-range interaction and the non-locality of the optical potentials are also considered. For optical-model parameters which describe the related elastic scattering results, an l = 2 neutron transfer was found to be most consistent with the data in all cases except for the transitions to the 1.760/1.852 MeV levels, which do not seem to proceed via a direct interaction. Relative spectroscopic factors have been determined and are in good agreement with a simple model in which 27Al and 26Al consist only of ( d 5 2 ) −1 and ( d 5 2 ) −2 configurations.

The elastic scattering of 5.5–10.0 MeV 3He particles by 27Al nuclei

Abstract Angular distribution for the elastic scattering of 5.5, 7.0, 8.0, 9.0 and 10.0 MeV 3 He particles by 27 Al nuclei have been measured for scattering angles between 15° and 165° in the laboratory system. The 5.5 MeV results are significantly different from those published by Parry et al. 1 ). The data have been analysed using simple optical model Woods-Saxon potentials.

The reaction 28Si(3He, α)27Si at E(3He) = 12 MeV

Angular distributions for the Si(3He, 3He)Si and the 28Si(3He, α)27Si reactions induced by 12 MeV 3He particles have been measured. The analysis in terms of the optical model and the DWBA has been carried out and the results are discussed in conjunction with other data for the neutron pick-up reactions from 28Si. Occupation numbers for neutrons in d52, d32 and S12 orbits are obtained for the ground state wave functions of 28Si and compared with the proton occupation numbers.

Energy dependence of the 16O(3He), 3He)16O and the 16O(3He, α0)15O angular distributions in the range 9.8–11.7 MeV

Abstract Angular distributions of the 16 O( 3 He, 3 He) 16 O and the 16 O( 3 He, α 0 ) 15 O reactions have been measured at the incident 3 He particle energies of 9.802, 9.995, 10.210, 10.313, 10.465, 10.720, 11.229 and 11.738 MeV. While the distributions for the elastic scattering are similar at all energies, the shape of the differential cross section for the 16 O( 3 He, α 0 ) 15 O reaction exhibit a strong energy dependence at angles θ ≧ 50° . At forward angles, the 3 He, α) distributions display some characteristics of direct pick-up transition, i.e. a rise in the differential cross section and a regular diffraction structure. The data have been analysed in terms of the optical model and distorted-wave Born approximation theory.

Optical-model ambiguities for 22Ne(3He, 3He)22Ne elastic scattering at 10 MeV

Abstract The angular distribution for the elastic scattering of 9.744 MeV 3 He particles by 22 Ne nuclei has been measured from 15° to 160° (lab). An optical-model analysis, using a central Woods-Saxon potential with volume absorption has indicated a continuous optical-potential ambiguity, which appears to be due to the strong dependence of the scattering on the nuclear surface.

Non-statistical effects in neutron capture γ-ray spectra

Abstract A search for non-statistical effects in γ-ray spectra following neutron capture has been made for incident neutron energies in the range 40 keV to 1 MeV. The experiments were performed using a 20 cm × 15 cm Nal detector; thirty elements ranging from calcium to uranium were examined. Marked non-statistical effects were found in the spectra from elements in the mass regions where the 3s, 3p and 4s neutron strength functions maximize. Results from the first two regions could often be explained in terms of enhanced transition strengths to final states with a strong single-particle nature.

Levels of 16O near 13 MeV excitation from 15N + P reactions

Abstract Angular distributions, a 0° excitation function and Doppler-broadened γ-ray profiles for the reaction 15 N(p, α 1 γ), and angular distributions for the 15 N(p, α 0 ) reaction, have been measured for proton energies from about 900 to 1250 keV. These data, together with analysing powers from the 15 N ( p , α 0 ) reaction, have been satisfactorily fitted by means of R -matrix theory in terms of the known levels of 16 O in the 13 MeV region together with background contributions.

Energy levels of 16O near 15 MeV excitation from 15N + p reactions

Abstract Measurements have been made of excitation functions and angular distributions of the 15N(p, p0), 15N(p, α0) and 15N(p, α1) reactions for bombarding energies between Ep = 2.88 and 3.64 MeV. A multi-level R-matrix analysis of the data has enabled the identification of 16O levels at excitation energies of ≈ 14.6 (1−), 14.92 (2+), 15.10 (0+), 15.19 (2−), 15.26 (2+) and 15.43 (3−) MeV.

A remeasurement of the 12C(α, γ0) excitation function in the vicinity of the 12.44 and 13.1 MeV levels of 16O

Abstract The excitation function of the 12 C(α, γ 0 ) reaction at θ = 90° has been remeasured for bombarding energies between 6.5 and 8.5 MeV. The measurement was made to resolve discrepancies apparent in earlier measurements relating to the absolute cross section, the location of the lower 1 − resonance near 7.05 MeV ( 16 O excitation energy 12.44 MeV) and to the relative peak cross sections of this resonance and a second 1 − resonance at 7.88 MeV.