Emission of low-energy electrons from slowN6+ions interacting with a Au surface

Low-energy electrons emitted during the interaction of ${\mathrm{N}}^{6+}$ ions with a Au surface were measured. The projectile energy was varied in a wide range from 90 eV to 60 keV. A single-stage spectrometer was used to achieve reliable electron measurements at energies as low as a few eV. The experimental data are compared with simulations based on the classical over-the-barrier model. For slow projectiles the observed low-energy electrons are attributed to autoionizing transitions in high Rydberg states of the projectile. The autoionization electrons provide a signature for the first deexcitation steps of hollow atoms formed above the surface.