Change of the 7Be electron capture half-life in metallic environments

For the electron capture of Be-7 in the metallic environments Pd and In the Be-7 half-life was observed to increase by 0.9 +/- 0.2 and 0.7 +/- 0.2%, respectively, while in the insulator Li2O it was unchanged within experimental error (all samples cooled to T = 12K). The observations are consistent with the predictions of the Debye plasma model applied to the quasi-free electrons in the metals.