Microscopic Analyses of the (proton, Alpha) Reaction on IRON-54 and IRON-56.

The ('54,56)Fe(p,(alpha))('51,53)Mn reactions have been studied using the high resolution beam facility of the University of Manitoba Cyclotron. The experiment was performed using proton beams with bombarding energies of approximately 40 MeV. Overall energy resolution in the (alpha)-spectra obtained was between 50 keV and 75 keV (FWHM). From these spectra, differential cross sections in the angular range 12.5(DEGREES) < (theta)(,cm) < 83(DEGREES) were extracted for states up to approximately four MeV excitation in ('51)Mn and ('53)Mn. In those cases in which a number of states lie close together, arguments are given concerning the extent to which each of the states may contribute in the observed peaks. Analysis was carried out in the context of the distorted wave Born approximation using the computer code DWUCK. The proton optical model potentials were taken from analyses previously reported in the literature and the geometry of the alpha particle potentials was constrained by the "well matching" criterion in order to improve the applicability of the DWBA theory. Alpha particle elastic scattering data available in the literature were refitted using a Woods-Saxon geometry with parameters imposed by "well matching". The imposition of a Woods-Saxon geometry (as opposed to a Woods-Saxon square geometry) resulted in relatively poor fits to the alpha particle elastic scattering data, but good fits to the (p,(alpha)) angular distributions were obtained. The microscopic formalism developed by Falk was used to examine those states for which wave functions have been reported. Good quantitative agreement between the experimental and the theoretical transition strengths was obtained for a number of states. On the other hand, poor agreement was obtained in several cases. This suggests that wave functions calculated using a wider basis than the f(,7/2) shell of even one particle in the p(,3/2) f(,5/2) p(,1/2) shells are needed in order to describe several of the low lying states in ('51)Mn and ('53)Mn.