Temperature dependence of the quadrupole interaction for 111In in sapphire

Perturbed angular correlation measurements of the hyperfine interaction of In-111 in sapphire show, that after implantation and annealing at 1000 degrees C, the fraction of undistrubed probe atoms exhibiting a Unique quadrupole interaction with nu(Q)=219(1) MHz (eta=0) varies between 50% at 4 K, 5% at 100 K and 80% at 973 K in a reversible manner. A possible explanation for this surprising behaviour is the influence of so-called 'after effects' following the EC-decay of In-111 to Cd-111. Immediately after the decay the Cd-111 is in an ionized state, then collects electrons from its surroundings and reaches the ground state. The different electronic configurations that arise during this relaxation process affect the amplitude (integral(u)) and the damping (delta(u)) of the unique quadrupole interaction.