The spectral absorption file (usually named with a .abs or .gas file extension) is used by the Classic Absorption model, which is commonly used with the Gas radiometry solver.

This file is used to describe the absorption of volume as a function of wavelength. Since this data is commonly used with gases or plumes (which can vary in concentration), the units of the absorption coefficients are for a given concentration and over a given optical path length.

Format Details

The file contains the spectral absorption as a function of frequency (in wavenumbers) in a simple, two column text file. The columns can be separated by any whitespace (spaces, tabs, etc.). The spectral samples must be ordered in decreasing order. The units of the absorption coefficients are inverse ppm meters or 1/ppm-m.

Example File

3700.000000     4.019800e-02
3699.500000     1.237900e-02
3699.000000     5.621300e-03
3698.500000     3.779900e-03
3698.000000     2.733500e-03
3697.500000     2.178500e-03
[lines deleted for documentation purposes]
502.120000      2.651600e-03
501.640000      3.204400e-03
501.160000      4.839500e-03
500.670000      8.929400e-03
500.190000      3.098300e-02
Note The spectral samples do not need to be on regular intervals.