Isomeric yield ratios and excitation functions in alpha -induced reactions on 107,109Ag.

Abstract

Isomeric yield ratios for the reactions $^{107}\mathrm{Ag}$(\ensuremath{\alpha},3n${)}^{108}$In, $^{107}\mathrm{Ag}$(\ensuremath{\alpha},\ensuremath{\alpha}3n${)}^{104}$Ag, $^{109}\mathrm{Ag}$(\ensuremath{\alpha},2n${)}^{111}$In, and $^{109}\mathrm{Ag}$(\ensuremath{\alpha},3n${)}^{110}$In are determined in the energy range of 20--63 MeV \ensuremath{\alpha} particles. Excitation functions for the above reactions as well as for the $^{107}\mathrm{Ag}$(\ensuremath{\alpha},2n${)}^{109}$In, $^{107}\mathrm{Ag}$(\ensuremath{\alpha},\ensuremath{\alpha}2n${)}^{105}$Ag, $^{109}\mathrm{Ag}$(\ensuremath{\alpha},4n${)}^{109}$In, $^{109}\mathrm{Ag}$(\ensuremath{\alpha},5n${)}^{108}$In, and $^{109}\mathrm{Ag}$(\ensuremath{\alpha},\ensuremath{\alpha}4n${)}^{105}$Ag reactions are also presented. Experimental excitation functions are compared with statistical model calculations taking into account precompound particle emission. Isomeric yield ratios are found to depend strongly on the root mean square orbital angular momentum in the entrance channel. A semiempirical method for the prediction of isomeric yield ratios failed to reproduce experimental data even for compoundlike reactions. Isomeric yield ratios were also calculated in the frame of a statistical model under consideration of angular momentum effects in the preequilibrium and the equilibrium stage. Overall agreement between the theory and the experiment for isomeric yield ratios was found to be satisfactory especially at low bombarding energy when compound nucleus reaction channel is dominant. The discrepancy observed at higher bombarding energies needs to be theoretically investigated in greater detail.