The total transmission function of the ACIS filters is finally described by the following expression,
For energies excluding the EXAFS regions the transmission function 
is given by
the fit of our simple model (Equation 2) that incorporates the atomic scattering
factors 
and 
as tabulated by Henke et al., (1993).
For energies within the EXAFS regions our model function 
includes in addition
the best fit model to the EXAFS regions.
The transmission data for the Imager and Spectroscopy filters, the model transmission function, and the percent difference between the model and data are presented in Figure 3 and Figure 4. The transmission function follows the data to better than 0.5% in non-EXAFS regions and better than 1% in the C-K and Al-K EXAFS regions. For energies within several eV of the absorption edges, larger deviations of a few percent are observed. These can be explained as a combination of the limits in the resolving power of the monochromator used in our measurements, the uncertainties in the atomic scattering factors near absorption edges, and the presence of resonance lines and narrow, near-edge X-ray absorption structure within several eV of the absorption edges.
Figure 3: Top Panel: X-ray transmission data of Imager filter with best fit
transmission model. Lower Panel: Percent difference between model fit and data.
Figure 4: Top Panel: X-ray transmission data of Spectrometer filter with best fit
transmission model. Lower Panel: Percent difference between model fit and data.
