Observation of Nuclear Excitation by Electron Transition in197Auwith Synchrotron X Rays and an Avalanche Photodiode

We have succeeded in observing nuclear excitation by electron transition (NEET) in ${}^{197}\mathrm{Au}$ by a new method. Monochromatic x-rays of synchrotron radiation were used to ionize the $K$ shell of gold atoms in a target foil. The internal-conversion electrons emitted from excited nuclei were detected with a silicon avalanche photodiode. At a photon energy of 80.989 keV, the NEET probability in ${}^{197}\mathrm{Au}$ was determined to be $(5.0\pm 0.6)\times {10}^{-8\mathrm{}}$ from a comparison of the event number per photon between NEET and the nuclear resonance at 77.351 keV.