Deexcitation dynamics of muonic atoms revealed by high-precision spectroscopy of electronic X rays

Okumura, Takuma*; Azuma, Toshiyuki*; Bennet, D. A.*; Caradonna, P.*; Chiu, I. H.*; Doriese, W. B.*; Durkin, M. S.*; Fowler, J. W.*; Gard, J. D.*; Hashimoto, Tadashi   ; Hayakawa, Ryota*; Hilton, G. C.*; Ichinohe, Yuto*; Indelicato, P.*; Isobe, Tadaaki*; Kanda, Sotaro*; Kato, Daiji*; Katsuragawa, Miho*; Kawamura, Naritoshi*; Kino, Yasushi*; Kubo, Kenya*; Mine, Kairi*; Miyake, Yasuhiro*; Morgan, K. M.*; Ninomiya, Kazuhiko*; Noda, Hirofumi*; O'Neil, G. C.*; Okada, Shinji*; Okutsu, Kenichi*; Osawa, Takahito  ; Paul, N.*; Reintsema, D.*; Schmidt, D. R.*; Shimomura, Koichiro*; Strasser, P.*; Suda, Hirotaka*; Swetz, D. S.*; Takahashi, Tadayuki*; Takeda, Shinichiro*; Takeshita, Soshi*; Tampo, Motonobu*; Tatsuno, Hideyuki*; Tong, X. M.*; Ueno, Yasuhiro*; Ullom, J. N.*; Watanabe, Shin*; Yamada, Shinya*

We observed electronic X rays emitted from muonic iron atoms using a superconducting transition-edge-type sensor microcalorimeter. 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, this data clearly reveals the electronic - and -shell hole production and their temporal evolution during the muon cascade process.