Incident ion energy effects on the secondary Rh⁺ ion kinetic energy and azimuthal angle distributions from Rh{111}

The nature of the collision cascade initiated by a bombarding ion beam strongly depends upon the kinetic energy of the ion beam. As the incident ion beam energy is lowered, the changes in the collision cascade cause a reduction in the total ejected particle yield, the ion fraction of the ejected particles, and the fraction of ejected clusters. We present the azimuthal angle and kinetic energy distributions of secondary Rh⁺ ions from a clean Rh{111} sample bombarded with 250 and 3000 eV Ar⁺ ion beams. These distributions show features associated with the lattice atomic arrangement and a previously unreported secondary ionization mechanism which arises from damage to the electronic structure of the lattice. The azimuthal angle and kinetic energy distributions exhibit substantial changes at low primary ion beam energy due to the diminution of the collision cascade.