Measurement of the $\beta^+$ and orbital electron-capture decay rates in fully-ionized, hydrogen-like, and helium-like $^{140}$Pr ions

TL;DR

This study measures decay rates of $^{140}$Pr ions with different electron configurations, revealing that ionization state significantly affects decay constants, which is crucial for understanding nuclear decay processes in highly ionized atoms.

Contribution

First measurement of $eta^+$- and electron capture decay rates in fully-ionized, hydrogen-like, and helium-like $^{140}$Pr ions, highlighting the influence of electron configuration on decay rates.

Findings

Hydrogen-like $^{140}$Pr$^{58+}$ decays faster than helium-like $^{140}$Pr$^{57+}$ by about 50%.

Ionized $^{140}$Pr$^{58+}$ decays faster than neutral atoms with 59 electrons.

Decay rates depend on electron configuration and angular momentum conservation.

Abstract

We report on the first measurement of the $\beta^+$- and orbital electron capture decay rates of $^{140}$Pr nuclei with the most simple electron configurations: bare nuclei, hydrogen-like and helium-like ions. The measured electron capture decay constant of hydrogen-like $^{140}$Pr$^{58+}$ ions is about 50% larger than that of helium-like $^{140}$Pr$^{57+}$ ions. Moreover, $^{140}$Pr ions with one bound electron decay faster than neutral $^{140}$Pr$^{0+}$ atoms with 59 electrons. To explain this peculiar observation one has to take into account the conservation of the total angular momentum, since only particular spin orientations of the nucleus and of the captured electron can contribute to the allowed decay.