The Absorption Cross Section of CI2 Molecule

Three published XS of CI2, by Burkholder [4], Marie [22] and JPL [23], were compared in order to check the consistency of these experimental XSs. This comparison is done in Table 6.1, using the fitted parameters obtained from Formula (29). These comparisons show that the parameters of the main S-S transition are in good agreement and those of the weak S-T transition are poorly determined for the JPL and Burkholder XS. 

It should be noted that two of these three XSs have very few data points and we cannot expect a good accuracy for the r parameter describing the asymmetry, even if the numerical uncertainty (Chi /DoF) of the fit is small. Note that the JPL data points are not the raw data but are determined from a fit of experimental data with a different analytic formula [23]. Below, the experimental XS of Marie [22] is used to test and compare the various approximations introduced in Sections 2 and 3 of this paper. 

FIGURE 6.1 Plot of the smoothed experimental CI2 Abs. Cross Section (XS/E) (full line), and the two contributions of the fitted XS/E the strong singlet-singlet (S-S) transition is dashed line, and the weak singlet-triplet (S-T) transition is a full gray line. The analytic forms and the parameters of the S-S and S-T components are given in Table 6.1, Fit-3. 

TABLE 6.1 Comparison of the fitted parameters for the three experimental XSs of Marie (1993), JPL (2002) and Burkholder (1983). The three fits have been performed with the same analytic expression which is the sum of two components the main singlet-singlet transition is described by Formula (29) and the weak singlet-triplet transition by a Gaussian. The low ChiVooF for the JPL XS of 17 is mainly due to the very low number (30 pts) of data points 

2 Gaussians Formula (12 ) Formula (29) with prefactor with prefactor without 

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