Small-scale density inhomogeneities in the case of parametric interaction of radiation with gaseous media

A one-exposure holographic method was used in a study of small-scale inhomogeneities of the density in gaseous media. A study was made of the dynamics of a thermal grating formed in gaseous SF₆ by a degenerate four-wave interaction of CO₂ laser pulses. The main mechanism destroying such a density grating was found to be a shift of gas particles under the influence of pressure gradients. The thermal grating deformation distorted the wavefront of the diffracted beam.