Direct observation of the double Auger decay of aKhole

The double Auger (DA) decay of a K hole has been observed directly by detecting the two emitted electrons in coincidence. The hole was created in ³⁷Cl following the electron-capture decay of ³⁷Ar. The probability of DA decay, per Auger decay, with the two electrons both having an energy greater than 250 eV was found to be 3.7±{}0.2%. The DA probability was found to decrease exponentially as the energy partitioning between the two electrons changed from the asymmetric case (E₁E₂) to the symmetric case (E₁≈E₂). The DA probability accounts for the bulk of the intensity of high charge states previously measured in ³⁷Cl.