Calculation of a Two-Electron-One-Photon Transition Rate for Fe

The transition rate for a correlated two-electron jump into the doubly ionized K shell of Fe followed by emission of only one photon has been calculated using many-body perturbation theory. The ratio of the rate for the usual one-electron-one-photon transition to that of the two-electron-one-photon transition was calculated to be 0.563×{}10⁴ in the length approximation and 0.586×{}10⁴ in the velocity approximation. These results compare favorably with the ratio of (0.4±{}0.3)×{}10⁴ measured recently by W\"olfli et al.