3pnpS1autoionization states of the magnesium atom

We present the result of a theoretical study of the $3pnp{}_{}{}^1{}_{}{}^{}S$ autoionization states above the first ionization threshold of the magnesium atom. By transferring the dominating configuration interaction between $3p^2$ and $3s^2$ configurations into the bound component of the state function of the autoionization state, the remaining interaction strength between the bound component and the background open channel can be represented by a second-order perturbation contribution in a simple application of the Fano procedure. The calculated width of the $3p^2{}_{}{}^1{}_{}{}^{}S$ state is found to be in excellent agreement with recent two-step two-color photoionization experiment.