Double $\mathit{K}$-Vacancy Production in Molybdenum by X-Ray Photoionization

We report the observation of double $K$-vacancy production in x-ray photoionization of molybdenum. From these data we deduce the relative probabilities for production of double and single $K$ vacancies by photon impact at 50 keV and report the most precise measure of the ratio of double to single $K$-vacancy production by photon impact in a heavy atom. That ratio provides an important probe of electron-electron correlations in high- $Z$ atoms where theoretical descriptions must consider those correlations simultaneously with relativity. Our results suggest the need for theoretical treatments to properly deal with such systems.