Shapes of Optical Emission Lines from Atoms Excited by Fast Ion Impact: I. Calculated Profiles

Abstract

After an inelastic collision between a neutral gas atom and a fast ion incident in a beam the excited gas atom emits radiation. The emitting gas atom has a variety of line-of-sight velocities relative to some fixed observer. This is a consequence of the kinematics of the collision and the angular dependence of the collision cross section. An expression for the intensity as a function of the frequency of the radiation is derived and then synthetic profiles for several viewing angles are obtained through numerical integration of this expression. Then the utility of the line profile as a means of determining the angular dependence of the inelastic collision cross section is examined.