If you use any of the non-relativistic data or associated programs linked on this page in a scientific publication, please refer to the following paper:

van Hoof P.A.M., Williams R.J.R., Volk K., Chatzikos M., Ferland G.J., Lykins M., Porter R.L., Wang Y.
Accurate determination of the free-free Gaunt factor, I -- non-relativistic Gaunt factors
2014, MNRAS, 444, 420

If you use any of the relativistic data or associated programs linked on this page in a scientific publication, please refer to the following paper:

van Hoof P.A.M., Ferland G.J., Williams R.J.R., Volk K., Chatzikos M., Lykins M., Porter R.L.
Accurate determination of the free-free Gaunt factor, II -- relativistic Gaunt factors
2015, MNRAS, 449, 2112

If you used merged relativistic data, please refer to both papers.

The free-free Gaunt factors as a function of ε_i and w can be found in the file gauntff_nonav.dat.

The thermally averaged free-free Gaunt factors as a function of γ² and u can be found in the file gauntff.dat.

Simple Fortran and C programs are available to interpolate the data in the non-averaged and thermally averaged Gaunt factor files linked above. These programs can work on either data file, but they are by default set up to work on the thermally averaged Gaunt factors. To interpolate on the non-averaged data, you need to uncomment line 42 (Fortran version) or line 45 (C version) before compiling.

Simple Fortran and C programs are available to interpolate the total free-free Gaunt factors. These programs do not need the data file linked above.

In van Hoof et al. (2015) we present calculations of the relativistic thermally averaged free-free Gaunt factor using the Bethe-Heitler-Elwert (BHE) approximation. However, these pure BHE data are not valid for low temperatures and/or low frequencies due to limitations of the BHE approximation. In this regime the non-relativistic (NR) data presented above should be used. We have therefore merged the pure BHE data with the NR data to obtain a data set that is valid over the entire range of the parameter space. This set is made available below.

Merged data

Simple Fortran and C programs are available to interpolate the data in the thermally averaged Gaunt factor files linked above (or the pure BHE files linked below). The programs are set up to interpolate on the merged Z=1 data set. In order to interpolate on other data sets, you need to change the file name on line 41 (Fortran version) or line 44 (C version).

Pure BHE data

Frequency integrated data

Simple Fortran and C programs are available to interpolate the total free-free Gaunt factors linked above. The programs are set up to interpolate on the merged Z=1 data set. In order to interpolate on other data sets, you need to change the file name on line 44 (Fortran version) or line 47 (C version).

All data files and interpolation programs shown above are copyrighted by the following BSD-style license.

The source code used to generate these data tables is available in the source directory. The source code is distributed under a different copyright (GPL v3).

P.A.M. van Hoof
Royal Observatory of Belgium
Ringlaan 3
B-1180 Brussels
Belgium
p (dot) vanhoof (at) oma (dot) be