RAINBOW SCATTERING FROM SOLID-SURFACES

Rainbow scattering from solid surfaces is discussed for beams of particles with energies from thermal to more than 1 MeV. The phenomenon of rainbow scattering is introduced. It is demonstrated to be a singularity in the classical scattering cross section. Both in two- and more-dimensional scattering problems rainbows are observed. In the latter case catastrophe theory can be used as a means to classify the rainbows. At thermal energies the rainbows are observed in scattering of notably He and Ne from corrugated surfaces. At hyperthermal energies rainbows are observed in both atom and ion scattering. At energies above 100 eV penetration of the solid by the beam particles occurs and rainbow scattering is not as pronounced and also less studied. In the case of scattering of molecules also rotational rainbows are observed. In this case the rainbow refers to a singularity in the classical excitation function for rotational excitation.