src.Atomic.Opacity.HIff_CrossSection

src.Atomic.Opacity.HIff_CrossSection(T, wl)[source]

return free-free cross section of a HI atom in LTE in unit of e-26 cm^2

Parameters

  • T (Temperature, [\(K\)]) –

  • wl (wavelength, [\(\AA\)]) –

Notes

from 1, 2.

HI free-free opacity in LTE is

kff = n_HI * HIff_CrossSection(T,wl) * 1e-26 (/cm)

  • n_HI: hydrogen number density in cm^(-3)

  • stimulated emission is corrected

  • partition function of HI is assumed to be 2.0, which is valid for T < 2.e4 K

Modification history:

  • 2019.9.15 K.Ichimoto from IDL ahic.pro

References

1

varnazza et al. (1976) ap.j.suppl. vol.30, 1.

2

porinomial fitting for f-f gaunt factor is taken from Carbon & Gingerich (1969) “theory and observation of normal stellar atmosphere” MIT press