Alignment of the 1s2p vacancy states of Ne doubly ionized by 700–2000-keV proton impact

The angular distribution of ${\mathit{KL}}_{23\mathrm{-}}$${\mathit{LLL}}_{23}$ Auger electrons emitted from the decay of 1s2p vacancy states of Ne doubly ionized by 700–2000-keV protons has been measured. From the measured anisotropy of the Auger lines the alignment of the double-vacancy states has been deduced. Our data compared with different theories indicate that the shake-off plays an important role in the double-ionization process at these energies.