Double-Core-Hole States in Neon: Lifetime, Post-Collision Interaction, and Spectral Assignment

Using synchrotron radiation and high-resolution electron spectroscopy, we have directly observed and identified specific photoelectrons from $K^{-2}V$ states in neon corresponding to simultaneous $1s$ ionization and $1s\to \text{valence}$ excitation. The natural lifetime broadening of the $K^{-2}V$ states and the relative intensities of different types of shakeup channels have been determined experimentally and compared to ab initio calculations. Moreover, the high-energy Auger spectrum resulting from the decay of ${\mathrm{Ne}}^{2+}{K}^{-2}$ and ${\mathrm{Ne}}^{+}{K}^{-2}V$ states as well as from participator Auger decay from ${\mathrm{Ne}}^{+}{K}^{-1}{L}^{-1}V$ states, has been measured and assigned in detail utilizing the characteristic differences in lifetime broadenings of these core hole states. Furthermore, post collision interaction broadening of Auger peaks is clearly observed only in the hypersatellite spectrum from $K^{-2}$ states, due to the energy sharing between the two $1s$ photoelectrons which favors the emission of one slow and one fast electron.

Figure 1

(a) $K^{-2}V$ photoelectron spectrum measured at 2.3 keV. The intensity of the spectrum is plotted as a function of binding energy. The red dots are the experimental points and the solid blue line is the result of the fit. The photoelectron peaks are identified and two different Rydberg series are observed, corresponding to direct ($1s^{-2}n{s}^1$) and conjugate ($1s^{-2}n{p}^1$) contributions (see text). (b) Calculated photoelectron spectrum—taking into account the angular distribution (see text)—and the individual direct (red bars) and conjugate (green bars) contributions.

Figure 2

Hypersatellite Auger spectrum of neon measured at 2.3 keV photon energy. The dots are the experimental data, the black line is the result of our fit, the dashed line represents the $KLL$ Auger Lorentzian tail. Four different contributions can be observed and the different-colored peaks in the bottom of the figure are the results of our fit: the blue peaks are hypersatellites of $K^{-2}$ states, the black peaks are the hypersatellites of $K^{-2}V$ states, the red peaks are the hypersatellites of $K^{-2}{L}^{-1}V$ and $K^{-2}{L}^{-1}$ states, and the green peaks are the participator Auger of $K^{-1}{L}^{-1}V$ states.

Figure 3

863–890 eV kinetic energy region of the hypersatellite Auger spectrum taken at $\mathrm{h}\nu =2.3\mathrm{keV}$. The red dots are the experimental data, the blue line is our fit and the solid black lines correspond to the functions used to fit the $K^{-2}V$ peaks at 880.5 and 881.5 eV. The inset is an enlarged view of the region of the hypersatellites of $K^{-2}V$ states.