Search for Oscillation of the Electron-Capture Decay Probability of $^{142}$Pm

TL;DR

This study searched for time modulation in the electron-capture decay of $^{142}$Pm to verify previous claims of oscillations, but found no such modulation at the reported levels, challenging earlier observations.

Contribution

The paper provides a high-precision experimental test that refutes prior claims of oscillatory decay behavior in $^{142}$Pm.

Findings

No oscillatory modulation detected at the claimed frequency.

Measured half-life consistent with accepted values.

Reanalysis of previous data shows no oscillations.

Abstract

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.