Nuclear excitation by electron capture followed by fast x-ray emission

TL;DR

This paper investigates how fast x-ray emission following electron capture in highly charged ions can significantly enhance nuclear excitation resonance strength, with implications for experimental detection and astrophysical plasma studies.

Contribution

It demonstrates that x-ray emission stabilizes the system and increases resonance strength in highly charged ions, a novel approach to nuclear excitation by electron capture.

Findings

Resonance strength can increase by up to two orders of magnitude.

X-ray decay prevents internal conversion, stabilizing the system.

Potential applications in measuring nuclear excitation and astrophysics.

Abstract

The resonance strength of the two-step process of nuclear excitation by electron capture followed by $\gamma$ decay of the nucleus can be significantly increased in highly charged ions if the resonant capture proceeds via an excited electronic state with subsequent fast x-ray emission. For fully ionized $^{238}_{92}\mathrm{U}$ and $^{232}_{90}\mathrm{Th}$, the {x-ray} decay stabilizes the system against internal conversion of the captured electron, with an increase of both nuclear lifetimes and resonance strengths of up to two orders of magnitude compared with the case when occupied atomic orbitals prevent the x-ray de-excitation. Applications of this effect to the measurement of the not yet experimentally observed nuclear excitation by electron capture and to dense astrophysical plasmas are discussed.