Evidence for nuclear excitation by electron transition on 193Ir and its probability

Nuclear excitation by electron transition (NEET) has been observed for 193Ir in K-shell photoionization, following a previous measurement for 197Au. We detected internal conversion electrons emitted by decaying excited nuclei of 193Ir in time spectroscopy using a silicon avalanche photodiode. The incident synchrotron X-rays were monochromatized and scanned around the iridium K-edge (ΔE=0eV). At energies of between ΔE=+105 and +344eV, an increase of event rates due to nuclear excitation was observed at a level of 2.2-times higher than the standard deviation of the background measured at energies of between ΔE=−3 and −324eV. The NEET probability at ΔE=+128eV was obtained to be (2.8±0.4)×10−9, which is less than one tenth of the probability for NEET on 197Au.