Influence of the molecular environment on the hyperfine interaction of Cd-111 ions in gaseous radioactive (InI3)-In-111

The hyperfine interaction (HFI) of Cd-111 in gaseous InI3 systems was studied using perturbed angular correlation (PAC) measurements. The electron capture decay of In-111 in InI3 followed by Coulomb fragmentation of the molecule produces an excited Cd-111 ion. The nucleus decays to the ground state via a gamma-gamma cascade the angular correlation of which is perturbed due to HFI. Collisions of the ion with InI3 molecules can strongly change the perturbation. The attenuation coefficient G(22)(infinity) varies between 0.09 and 0.87 for molecular densities between 10(14) and 10(20) cm(-3). G(22)(t) shows a similar behavior. The present investigation has yielded an unexpected temperature dependence of the perturbation that had not been observed in previous experiments with InI, InCl and InCl3 systems. A possible explanation is that the ion's charge may be lower if the In-111 atom was part of a dimeric (In2I6) molecule before decay.