Abstract: The free-free i.e. electron-ion inverse “Bremsstrahlung” characteristics are determined for the case of the solar atmosphere as well as solar interior where such plasma characteristics as plasma density and temperature change in wide region. We demonstrate that determination of these characteristics such as the absorption coefficients and Gaunt factors can be successfully performed in the whole diapason of electron densities and temperatures which is relevant for the corresponding atmosphere model. The used quantum mechanical method of the calculation of the corresponding spectral absorption coefficient and Gaunt factor is described and discussed in details. The results are obtained for the case of a solar photosphere and solar interior model in the wavelength region 10 nm ≤λ≤3000 nm. The range of the physical parameters covers the area important for plasma modeling from astrophysical standpoint (white dwarfs, central stars of planetary nebulae, etc). Also, these results can be of interest and use in investigation of different laboratory plasmas.