A 3-AXIS GONIOMETER IN AN UHV MOLECULAR-BEAM EXPERIMENT

A sample manipulator with six degrees of freedom, which is part of a m olecular beam scattering apparatus used to study gas-surface interacti ons, is described. Incidence parameters such as the angle of incidence and the azimuthal angle can be set and particles leaving the surface both in and out the plane of incidence can be measured (to within 0.1 degrees accuracy). The latter is achieved, under computer control, by a combination of the movement of the manipulator and the movement of t he detector. Cooling of the sample to liquid N-2 temperatures and heat ing to at least 1600 K is possible. A mathematical relation among the positions of the manipulator and of the detector, the required inciden ce angle of the particles and the final angle of the scattered particl es to be measured is derived.