3He-induced reactions on cobalt

Abstract

3He-induced reactions on the target element cobalt were investigated in the energy region from 14 to 130 MeV using the stacked-foil technique. 19 excitation functions were measured for the production of 61Cu, 57Ni, 60m+gCo, 58m+gCo, 57Co, 56Co, 55Co, 59Fe, 56Mn, 54Mn, 52Mn, 51Cr, 48Cr, 48V, 48Sc, 47Sc, 46m+gSc, 44mSc. The new cross sections are in extreme disagreement with the earlier determinations which were restricted to the nuclides 61Cu, 58m+gCo, 57Co and 56Co and to energies below 40 MeV. The experimental data are compared with “ a priori” calculations considering equilibrium as well as preequilibrium reactions. The excitation functions exhibit strong preequilibrium effects over wide ranges. From the reaction 59Co( 3He, n) 61Cu an initial exciton configuration of n 0 = 4(1n-3p-0h) is deduced. The theoretical predictions reveal severe shortcomings with respect to reactions as ⦅( τ, 2p xn), x = 0, 2, 3⦆, (τ, 3p) and (τ, 4p2n). For the explanation of the observed discrepancies break-up of the incoming 3He particle as well as double stripping may be assumed. Moreover, contributions of preequilibrium α-emission were to be seen giving rise to discrepancies between theory and experiment in the low-energy part of the excitation functions. The results indicate that the initial states of 3He-induced reactions are more complicated than assumed by the present forms of preequilibrium theories. It is concluded that it is not possible by today's reaction theories to perform “ a priori” calculations of integral excitation functions with the accuracy needed for the various purposes of application.