Energy Spectra of Protons from (d, p) Reactions in Heavy Elements

Abstract

Surveys of proton energy distributions from ($d, p$) reactions were made on nuclei with $Z>\mathrm{}30\mathrm{}$ using resolutions of 500 and 80 kev. The gross structure shows broad peaks due to the major nuclear shells, as expected from the fact that ($d, p$) stripping reactions excite single-particle states; peaks due to the subshell structure can be seen in some cases, especially in the heavier nuclei. The energies of the various peaks do not shift from element to element in the manner expected from simple theory; it is shown that this is not in conflict with neutron cross-section evidence, and possible explanations are proposed. The energy spacing between major shells derived from these measurements allows calculation of the reduced mass for nucleons in nuclei; the result is very different from the predictions of Brueckner theory, but explanations for this discrepancy are advanced. The results and their interpretation given here are in direct conflict with the Wilkinson theory of gamma-ray giant resonances. The energy spectra are very similar at different angles, which indicates that the stripping process is predominant at all angles. Deviations from Butler angular distribution theory at large angles must therefore be due to difficulties in that theory rather than due to the onset of competing process.