Interaction potentials for Na, Al and Ar atoms from rainbow scattering under axial surface channeling from Al(1Â 1Â 1) and Al(0Â 0Â 1) surfaces

Na, Al and Ar atoms with energies ranging from 3 to 80 keV are scattered from Al(1 1 1) and Al(0 0 1) surfaces under axial surface channeling conditions. Well defined peaks in the angular distributions for scattered projectiles are attributed to “rainbow-scattering” and are analyzed in terms of the effective scattering potential. Computer trajectory simulation of the rainbow angles with established pair potentials leads to good agreement for potential energies above about 30 eV. At smaller potential energies we observe pronounced deviations for the three different projectile atoms which are attributed to an additional contribution to the overall potential due to the effect of embedding the atoms into the electron gas in front of the metal surface. Taking into account this additional potential leads to a consistent description of data.