(t→,p) reaction onFe56,Ni58,60,64: Structure and reaction-mechanism effects

Abstract

Differential cross sections and analyzing powers have been measured for the ($\stackrel{\ensuremath{\rightarrow}}{t}$,$p$) reaction on $^{56}\mathrm{Fe}$, $^{58,60,64}\mathrm{Ni}$ at an incident energy of 17 MeV. Data were obtained for states up to an excitation of 3.7, 3.13, 2.8, and 4.9 MeV in $^{58}\mathrm{Fe}$, $^{60,62,66}\mathrm{Ni}$, respectively, including about ten states each with spin and parity ${0}^{+}$, ${2}^{+}$, and ${4}^{+}$, and two states each with ${3}^{\ensuremath{-}}$ and ${5}^{\ensuremath{-}}$. The measured analyzing powers show angular distributions characteristic of the $L$ transfer, with variations from state to state comparable to those observed for cross sections of a given $L$. Angular distributions of the differential cross sections for strong transitions were generally fitted well by a standard distorted-wave Born approximation calculation. There appear to be significant discrepancies between the data and distorted-wave Born approximation predictions for excited ${0}^{+}$ states and for most ${4}^{+}$ states. Distorted-wave Born approximation predictions of analyzing power were in qualitative agreement with the data for ground-state transitions and for strong $L=2$ transitions but this was not true for $L=0$ transitions to excited states and for transitions with $L>2$. The effect of varying the optical parameters used in the distorted-wave Born approximation calculations was investigated; it was found that predictions of analyzing power for $L>0$ were quite sensitive to the choice of proton potential. The effects of two-step reaction processes were also investigated. These were found to produce large changes in predicted cross sections and analyzing powers, which could account for some of the discrepancies between these results and distorted-wave Born approximation predictions.NUCLEAR REACTIONS $^{56}\mathrm{Fe}$,$^{58,60,64}\mathrm{Ni}$($\stackrel{\ensuremath{\rightarrow}}{t}$,$p$) $E=17$ MeV; polarized beam; enriched targets; measured $\ensuremath{\sigma}({E}_{p},\ensuremath{\theta})$, ${A}_{y}({E}_{p},\ensuremath{\theta})$; DWBA; coupled reaction channel analysis.