Pressure Broadening and Laser-Induced Spectral Line Shapes
Journal
Advances in Atomic and Molecular Physics
Journal Volume
25
Journal Issue
C
Pages
133-162
Date Issued
1989
Author(s)
Sando, K.M.
Abstract
Doppler broadening is due to the higher frequencies of radiation absorbed or emitted by an atom moving toward an observer than by one moving away. The random component of velocity in the direction of the observer found in an equilibrium gas thus leads to broadening and a Gaussian line shape. Pressure broadening is due to collisions of the active atom with perturbing atoms, molecules, or heavy ions. Stark broadening is due to fluctuating electric fields due mainly to electrons in plasma. The line shape function is normalized to unity and can be regarded as a probability distribution. An important point is that if two broadening mechanisms are independent, the line shape resulting from the operation of both mechanisms is simply the convolution of the two line shapes resulting from each mechanism separately. Whereas quantum mechanical line shapes are most easily expressed and calculated in the frequency domain, classical path formulas are more readily obtained in the time domain. They result from solutions of the time dependent Schrödinger equation using a trajectory which is a classical path on a potential energy surface. © 1988 Academic Press Inc.
SDGs
Type
journal article