Abstract
We observed electronic x rays emitted from muonic iron atoms using superconducting transition-edge sensor microcalorimeters. The energy resolution of 5.2 eV in FWHM allowed us to observe the asymmetric broad profile of the electronic characteristic and x rays together with the hypersatellite x rays around 6 keV. This signature reflects the time-dependent screening of the nuclear charge by the negative muon and the -shell electrons, accompanied by electron side feeding. Assisted by a simulation, these data clearly reveal the electronic - and -shell hole production and their temporal evolution on the 10–20 fs scale during the muon cascade process.
- Received 12 February 2021
- Accepted 11 June 2021
DOI:https://doi.org/10.1103/PhysRevLett.127.053001
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