We have searched for time modulation of the electron capture decay probability of $^{ 142}$Pm in an attempt to confirm a recent claim from a group at the Gesellschaft f\"{ u}r Schwerionenforschung (GSI). We produced $^{ 142}$Pm via the $^{ 124}$Sn($^{ 23}$Na, 5n)$^{ 142}$Pm reaction at the Berkeley 88-Inch Cyclotron with a bombardment time short compared to the reported modulation period. Isotope selection by the Berkeley Gas-filled Separator is followed by implantation and a long period of monitoring the $^{ 142}$Nd K$_{ \alpha}$ x-rays from the daughter. The decay time spectrum of the x-rays is well-described by a simple exponential and the measured half-life of 40.68(53) seconds is consistent with the accepted value. We observed no oscillatory modulation at the proposed frequency at a level 31 times smaller than that reported by Litvinov { \it et al.} (Phys. Lett. B 664 (2008) 162; arXiv:0801.2079 [nucl-ex]). A literature search for previous experiments that might have been sensitive to the reported modulation uncovered another example in $^{ 142}$Eu electron-capture decay. A reanalysis of the published data shows no oscillatory behavior.
Categories: nucl-ex