Line shapes in resonance fluorescence for external sources near unit optical depth

Abstract

The angle-dependent resonant scattering line shape is calculated for a two-state atomic gas with a kinetic temperature similar to that of an external beam source for optical depths of less than or equal to unity. It is demonstrated that narrowing of the backscattered line shape occurs for all source temperature to absorber temperature ratios. It is also shown that there is no appreciable broadening when the source and absorption temperatures are different. The small amount of broadening that does occur is due to an enhancement of scattered radiation at frequencies away from the resonance-line centre frequency.Rocket-based resonance lamp measurements of atomic oxygen concentrations are complicated by the height-dependent optical depth for the 130.2, 130.4, and 130.6 nm oxygen emissions as well as by the nodification of the local environment and relative positions of the emission and absorption line shapes due to the motion of the rocket vehicle through the atmosphere.