Observation of Non-Exponential Orbital Electron Capture Decays of Hydrogen-Like $^{140}$Pr and $^{142}$Pm Ions

TL;DR

This study observes time-modulated electron capture decays in hydrogen-like $^{140}$Pr and $^{142}$Pm ions, revealing non-exponential decay behavior potentially due to neutrino mass eigenstate superpositions.

Contribution

First experimental evidence of non-exponential, time-modulated electron capture decays in hydrogen-like ions, suggesting neutrino interference effects.

Findings

Decay modulation period of about 7 seconds observed

Decay behavior deviates from standard exponential decay

Potential link to neutrino mass eigenstates superposition

Abstract

We report on time-modulated two-body weak decays observed in the orbital electron capture of hydrogen-like $^{140}$Pr$^{59+}$ and $^{142}$Pm$^{60+}$ ions coasting in an ion storage ring. Using non-destructive single ion, time-resolved Schottky mass spectrometry we found that the expected exponential decay is modulated in time with a modulation period of about 7 seconds for both systems. Tentatively this observation is attributed to the coherent superposition of finite mass eigenstates of the electron neutrinos from the weak decay into a two-body final state.