#### Abstract

Monochromatic x rays have been used to explore the phenomenon of nuclear excitation by electronic transition (NEET) in the ${}^{189}\mathrm{Os}$ atomic/nuclear system. A new theoretical approach to calculating this process has also been developed and predicts a value for the “NEET probability,” ${P}_{\mathit{NEET}},$ of $1.3\times {10}^{-10}.$ ${P}_{\mathit{NEET}}$ is the probability that a given atomic excitation (in this case a *K* vacancy), will result in the excitation of a specific nuclear state (in this case the 69.5-keV level in ${}^{189}\mathrm{Os}).\mathrm{}$ This value is much lower than most of the calculated values given in the literature for this system. Our measurement gives the result ${P}_{\mathit{NEET}}<9\mathrm{}\times {10}^{-10},$ an upper limit which is several orders of magnitude lower than the values found in previous measurements, but which is consistent with the new calculation.

DOI: http://dx.doi.org/10.1103/PhysRevC.61.051304

- Received 28 January 2000
- Published 21 April 2000

© 2000 The American Physical Society