Abstract
To investigate the nuclear transmutation of Cs into Pr reported in this journal by Iwamura and coworkers, we have measured the amount of Pr atoms in the range as low as ∼1×1010 cm-2 using inductively coupled plasma mass spectrometry for Cs-ion-implanted Pd/CaO multilayer complexes before and after deuterium permeation. The amount of Pr was initially at most 2.0×1011 cm-2 and it increased up to 1.6×1012 cm-2 after deuterium permeation. The increase in the amount of Pr could be explained neither by deuterium permeation-stimulated segregation of Pr impurities nor by external contamination from the experimental environment during the permeation. No increase in Pr was observed for permeation with hydrogen. These findings suggest that the observed increase in Pr with deuterium permeation can be attributed to a nuclear origin, as reported by Iwamura and coworkers, although the amount of the increase in Pr is two orders of magnitude less than that reported by them.