Beam-Foil-Gas Spectroscopy: A Technique for Studying Steady-state Non-equilibrium Processes

Abstract
When a thin foil is inserted in the beam of a beam-gas experiment the beam particle state populations are driven far from their beam-gas equilibrium values. Downstream from the foil the "new beam" and gas species interact to produce a new equilibrium, usually different from the beam-gas one. We present experimental results to demonstrate this effect and show how relative cross-section measurements can be used to study the beam-foil interaction.