Interatomic Coulombic decay following Ne $1s$ Auger decay in NeAr

Using momentum-resolved electron-ion multicoincidence spectroscopy, we have investigated interatomic Coulombic decay (ICD) in the heteronuclear NeAr dimer following Ne $1s$ Auger decay. The measured intensity ratio for the three ICD transitions Ne${}^{2+}$($2s^{-1}2p^{-1}\hspace{0.5em}{}^{1}P$)Ar to Ne${}^{2+}$($2p^{-2}\hspace{0.5em}{}^{1}S$)–Ar${}^{+}$($3p^{-1}$), Ne${}^{2+}$($2s^{-1}2p^{-1}\hspace{0.5em}{}^{1}P$)Ar to Ne${}^{2+}$($2p^{-2}\hspace{0.5em}{}^{1}D$)-Ar${}^{+}$($3p^{-1}$), and Ne${}^{2+}$($2s^{-1}2p^{-1}\hspace{0.5em}{}^{3}P$)Ar to Ne${}^{2+}$($2p^{-2}\hspace{0.5em}{}^{3}P$)-Ar${}^{+}$($3p^{-1}$) reasonably agree with predictions. The kinetic energy release distribution for the fragmentation to Ne${}^{2+}$($2p^{-2}\hspace{0.5em}{}^{1}D$)-Ar${}^{+}$($3p^{-1}$) after the ICD transition from singlet Ne${}^{2+}$($2s^{-1}2p^{-1}\hspace{0.5em}{}^{1}P$)Ar state, which is a mirror image of the kinetic energy distribution of the emitted ICD electrons, suggests that the corresponding ICD rate is roughly two times lower than predicted by ab initio calculations.

Figure 1

NeAr ion-ion coincidence TOF spectrum.

Figure 2

Panel (a) Kinetic energy release (KER) for Ne${}^{2+}$–Ar${}^{+}$ fragmentation channel. Panel (b) Kinetic energy distribution of electrons detected in coincidence with Ne${}^{2+}$–Ar${}^{+}$ pairs. Panel (c) Correlation map between electron emission and KER. The three straight diagonal lines correspond the energies of the ICD transitions: (1) Ne${}^{2+}$($2s^{-1}2p^{-1}\hspace{0.5em}{}^{3}P$)Ar to Ne${}^{2+}$($2p^{-2}\hspace{0.5em}{}^{3}P$)-Ar${}^{+}$($3p^{-1}$), (2) Ne${}^{2+}$($2s^{-1}2p^{-1}\hspace{0.5em}{}^{1}P$)Ar to Ne${}^{2+}$($2p^{-2}\hspace{0.5em}{}^{1}S$)-Ar($3p^{-1}$), and (3) Ne${}^{2+}$($2s^{-1}2p^{-1}\hspace{0.5em}{}^{1}P$)Ar to Ne${}^{2+}$($2p^{-2}\hspace{0.5em}{}^{1}D$)-Ar($3p^{-1}$). The signal at $~19$ eV electron energy corresponds to the Ne $1s$ photoelectron peak.

Figure 3

The distribution of the sum of electron kinetic energy in Fig. 2a and KER in Fig. 2b. Results of the fitting procedure discussed in the text are shown by solid curves.

Figure 4

The KER distributions for the ICD channels (1), upper panel, and (3), lower panel, presently measured and computed in different approximations. The theoretical spectra are convolved with the Gaussian function of 0.7 eV FWHM representing the experimental KER resolution. The computed relative intensities and measured spectra (in counts) are normalized at each maxima. The statistical errors for the measured data (not shown) are equal to square root from the number of counts.