Dependence of the K x-ray energy upon the mode of excitation

Abstract

The energy of the Ta Kα x rays emitted after electron capture of 181W has been observed to be lower by 0.79±0.06 eV compared to the fluorescent Ta Kα x rays. Similarly, it was found that the Ta Kα x rays emitted after internal conversion following β decay of 181Hf were higher by 0.7±0.1 eV in energy compared to the same fluorescent Ta x rays. The observed effects cannot be explained by the known mechanisms of chemical shift, hyperfine effects, isomer shifts, and shake-off effects alone. Similar observations of the K-x-ray energy shifts in the electron-capture decays of 153Gd and 175Hf with the corresponding fluorescent x rays in Eu and Lu, respectively, can be accounted for by the hyperfine effects, isotope shifts, and chemical shifts.