Electronic-state–lifetime interference in the hard-x-ray regime: Argon as a showcase

Electronic-state–lifetime interference is a phenomenon specific for ionization of atoms and molecules in the hard-x-ray regime. Using resonant $K{L}_{2,3}{L}_{2,3}$ Auger decay in argon as a showcase, we present a model that allows extracting the interference terms directly from the cross sections of the final electronic states. The analysis provides fundamental information on the excitation and decay processes such as probabilities of various decay paths and the values of the dipole matrix elements for transitions to the excited states. Our results shed light on the interplay between spectator, shake-down, and shake-up processes in the relaxation of deep core-hole states.

Figure 1

Cross sections of the final states $2p^{-2}n{p}^{+}$ ($4\le n\le 7$) plotted as a function of the photon energy relative to the ionization potential. The circles are the experimental points and the lines are the fitting results. The vertical lines indicate the energies of the resonantly excited intermediate states $1s^{-1}m{p}^{\prime }$ ($4\le m\le 9$).

Figure 2

Cross section of the $2p^{-2}6p^{+}$ final state plotted as a function of the photon energy relative to the ionization potential. The circles are the experimental points, the thick solid gray line is the fitting result. The thin solid blue, thick dashed red, and thin dashed green lines show the contributions of the spectator decay, the decay accompanied by a shake-up process from the $5p$ orbital, and the decay involving a shake-down process from the $7p$ orbital, respectively. The interference cross terms between the $1s^{-1}6p^{\prime }$ and $1s^{-1}5p^{\prime }$ electronic states and between the $1s^{-1}6p^{\prime }$ and $1s^{-1}7p^{\prime }$ electronic states are shown with thick dash-dotted red and thin dash-dotted green lines, respectively.

Figure 3

Experimental (top curve) and reconstructed (bottom curve) PEY. The bars under the reconstructed PEY indicate the intensities of the $1s-mp$ absorption transitions ($4\le m\le 7$), extracted from the fitting procedure; the solid line is the sum of the discrete contributions and the continuum contribution fitted with an arctangent function.