A study of the (₉Be, ₁₀B) reaction

• Main Author: Winfield, John Stuart
• Other Authors: Jelley, Nicholas Alfred
• Published: University of Oxford 1983
• Subjects: 539.7; Elastic scattering : Heavy ions : Inelastic scattering : Angular distribution (Nuclear physics)
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.347100

Angular distributions have been measured for the (⁹Be, ¹⁰B₀, ₁) reactions on ⁶³Cu, ⁵⁴Fe, ^26,24Mg and ¹⁶O at 43 MeV and on ⁴⁰Ca at 45 and 30 MeV. Several of these experiments were performed with the Oxford MDM-2 spectrometer and the design and testing of its 30 cm focal plane detector, which is of the "hybrid" type, is described. Despite the size of the counter, in particular the large cathode to Frisch-grid separation, the resolution of the ionization signals is comparable with that of smaller counters. The position resolution is < 0.6 mm. Optical potentials have been obtained from the measured elastic scattering of ⁹Be from ¹⁶O, ²⁶Mg and ⁴⁰Ca, and ¹⁰B from ²⁵Mg and ³⁹K. The exact finite-range DWBA calculations have generally well reproduced the shape of the experimental reaction cross-sections. However, inconsistencies of up to 50% between the extracted spectroscopic factors for ¹⁰B₀ and ¹⁰B₁ have been found. This anomaly was found insensitive to changes in either optical potential or bound state parameters. A new method of form factor calculation is described that uses a shell model potential in conjunction with a surface-peaked potential, the depth of which is adjusted to give the correct asymptotic form to the wavef unctions. Whilst this form factor showed some success, it did not account for the ¹⁰B₀/¹⁰B₁ anomaly. Collective model DWBA analyses of the inelastic excitation of the first 2⁺ state in ²⁶Mg and 3^- state in ⁴⁰Ca have given values for deformation parameters in reasonable agreement with light-ion work. A CCBA analysis of the ²⁶Mg 2⁺ state was carried out to estimate the effect of the coupling. Calculations performed for a two-step reaction process through inelastic excitation of a strongly coupled 5/2^- state in the projectile showed that this indirect route is important, but it could not solve the ¹⁰B₀/¹⁰B₁ problem alone. The conclusion is that other routes (projectile or target excitation) must be included.