New Test of Modulated Electron Capture Decay of Hydrogen-Like $^{142}$Pm Ions: Precision Measurement of Purely Exponential Decay

Abstract

An experiment addressing electron capture (EC) decay of hydrogen-like 142 Pm 60+ ions has been conducted at the experimental storage ring (ESR) at GSI. The decay appears to be purely exponential and no modulations were observed. Decay times for about 9000 individual EC decays have been measured by applying the single-ion decay spectroscopy method. Both visually and automatically analysed data can be described by a single exponential decay with decay constants of 0.0126(7) s −1 for automatic analysis and 0.0141(7) s −1 for manual analysis. If a modulation superimposed on the exponential decay curve is assumed, the best fit gives a modulation amplitude of merely 0.019(15), which is compatible with zero and by 4.9 standard deviations smaller than in the original observation which had an amplitude of 0.23(4).

The Nested_fit Data Analysis Program

“…In 2008 it was observed an unexpected modulation in the two-body electron capture decay of single H-like 142 61 Pm ions to the stable 142 60 Nd bare nucleus, with a monochromatic electron-neutrino emission [13]. The same modulation frequency, but with much smaller amplitude, was found in 2010 data [14] but not in the latest campaign in 2014 [15] where much more events have been recorded.…”

“…Nested_fit has been developed over the past years for the analysis of several sets of atomic experimental data that strongly contribute to the code evolution. We would like to mention in particular the analysis of low-statistics X-ray spectra of He-like uranium [5,17], X-ray spectra of pionic atoms [18,19], electron photoemission spectra from nano-particles [20,21], single-ion decay spectra [15] and response function of crystal X-ray spectrometers (in progress).…”

“…These two aspects reflect the difficulty to treat this problem where the acquired data are not sufficient to provide a marked preference for one model with or without modulation (see Ref. [15] for a more extended discussion). Even if apparently unsatisfying, this result avoid however possible over-interpretation of the data commonly encountered when classical methods are employed, as recently discussed in Ref.…”