Dicke narrowing as an example of line mixing

In the preceeding paper it was shown that the general problem of spectral l ine shapes in multiline, IR spectra may be determined by solving a transpor t relaxation equation far the off-diagonal elements of the density matrix. This is a semiclassical equation at the Wang-Chang-Uhlenbeck level, i.e., i t treats the quantized internal states as nondegenerate. Hen we apply the m aster equation to the case of Dicke narrowing, and by discretizing the velo city distribution show that Dicke narrowing of a single line may be treated in exactly the same manner as line mixing. Both effects lead to a narrowin g of a spectral distribution. We indicate how the numerical technique can b e extended and used to calculate profiles in the general case of spectra wi th speed-dependent broadening, shifting, and line mixing. [S1050-2947(99)11 305-2].