Velocity changing collisions in saturation absorption of U

Abstract

A systematic study of the 591.5 nm 238U lineshape of saturation absorption spectroscopy, including velocity changing collisions, was performed. The results indicate that for a light-mass perturber (He) the lineshape is composed of an exponential superimposed on a Gaussian background. For a heavy-mass atom perturber (Xe) the lineshape is a Lorentzian superimposed on a Gaussian background. In both cases the background Gaussian width is narrower than the Doppler width and its relative amplitude depends on the perturber's pressure. A comprehensive theoretical model, which takes into account both weak and strong collisions, is outlined. The model predicts the two types of lineshape and the agreement with the experimental results is excellent.