PX282 - C9g - combined opacity

image: iglesias & rogers (1996)

• three key zones are seen

• $(1):$ low temperatures

  • $H^{-}$ opacity rises steeply as the number of free electrons rises with $T$, which are needed to make $H^{-}$
  • this is a combined opacity, ie: average across wavelength and opacity sources

• $(2):$ medium temperatures, $T\sim {10}^{5}K$,

  • the decay comes from kramer's law: $\kappa \propto \rho T^{\frac{-7}{2}}$
  • driven by b-f and f-f absorption

• $(3):$ high temperature

  • all electrons are free, and everything is ionized
  • converges to a constant equivalent to the thomson scattering coefficient