Probability of nuclear excitation by electron transition in Os atoms

Abstract

An experiment on nuclear excitation by electronic transition (NEET) induced by deexcitations of the excited atomic states was performed on ${}^{189}\mathrm{Os}.$ Osmium targets were bombarded with both a white beam and with a monochromatic 115 keV x ray beam to produce K vacancies in Os atoms. Online K x-ray spectra were measured with a Ge detector and the L x rays emitted from the 30.814 keV isomer state in the ${}^{189}\mathrm{Os}$ nucleus were measured offline. The NEET probability obtained from the monochromatic beam experiment was deduced to be less than $4.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ per created K hole. This value is much lower than the values measured so far. The white beam experiment shows that these high probabilities of the NEET process in ${}^{189}\mathrm{Os},$ which were obtained by irradiation with white x-ray and bremsstrahlung x-ray beams, results mainly in a contribution from direct nuclear photoabsorption into the 69.537 keV state in ${}^{189}\mathrm{Os}.$