Low-Energy Protons Produced in the Deuteron Bombardment of Nuclei

Abstract

When nuclei are bombarded by fast deuterons a continuous spectrum of protons is observed at energies corresponding to Q< -2.2 Mev. The shape and angular distribution of this continuum were studied for several targets, from Li to Au, with 14.8-Mev deuterons. The angular distributions are strongly peaked at or close to 0° for light elements; for heavy elements the peak broadens and moves to ^50°. The energy spectra shows a peak which, with increasing angle moves to lower energies for light elements, and moves to higher energies for heavy elements. All features of the results are explained using a semiclassical theory in which the deuteron is broken up in the external field of the nucleus. The breakup occurs at or near the nuclear surface for light elements, but quite far out from it in heavy elements. Observed cross sections are far larger than theoretical predictions for either Coulomb or nuclear breakup.

Phenomenological model for light-projectile breakup

“…Some evidence of a similar peak is also seen in the cadmium data from Ref. [6] at forward angles. This suggests a possible contribution from a breakup mechanism where both fragments are emitted at very nearly the projectile velocity.…”

“…The results for deuteron breakup at 14.8 MeV [6] and 56 MeV [8] do not extend to backward angles, and there is no sign of this peak in the data [17] for 70 and 80 MeV deuterons. DWBA calculations [15] that include both breakup and direct stripping show a backward-angle tail in the double-differential cross section near the energy of the breakup peak, but the energy spectrum of this tail (shown only for a thorium target) is more typical of direct stripping.…”

“…The published graph of the platinum data at 14.8 MeV [6] is easier to read, but the data cut off above an emission energy of 12.5 MeV, which is lower than for the other targets. Because the energy of the breakup peak is also higher, there is no clean region for estimating the continuum at the high energy end of the spectrum.…”

“…The points show the data from Ref. [6], the dashed curves show the calculated breakup peaks, the dotted curves show estimates of the underlying continuum, and the solid curves show the total estimated spectra.…”

“…Refs. [1,3,[6][7][8][9][10][11]). However, they must typically make assumptions about details of the reaction mechanism that are not well understood and that become more complex as the mass of the projectile-and therefore the number of possible breakup channels-increases.…”