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

摘要

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