Experimental investigation of the interatomic Coulombic decay in NeAr dimers

The kinetic-energy distribution of interatomic and -molecular Coulombic decay (ICD) electrons emitted following photoionization of $2s$ electrons from Ne atoms in NeAr dimers has been measured in a synchrotron radiation experiment with a velocity-map-imaging photoelectron-photoion-coincidence spectrometer. The position of the peak of the experimental distribution agrees well with calculations. The broadening of the distribution to high energies with respect to calculations of the ICD spectrum of the NeAr $v=0$ ground state is explained by the contribution to the spectrum due to the population in the excited vibrational states $v=1$ and $v=2$ of the electron ground state. On the other hand, the broadening on the low-energy side of the measured distribution may be explained by the dimer contracting in the intermediate state before ICD occurs, electrons coming from the ICD to spin-orbit split excited ion states, or a combination of these effects.