The Escape of Resonance-Line Radiation from Extremely Opaque Media

`A7e consider the escape of resonance-line radiation from a low-density medium in which photon destruction processes are negligible. Numerical solutions are presented for media with large enough linecenter optical depths r5 that the effects of the damping wings dominate. The numerical results show that the mean number of scatterings (N T in this limit, rather than (N as predicted by Osterbrock. Further, the results show that (N; is independent of the value of the damping constant a. These results can be understood if the photons escape in a sin gte longest excttrsion during which they are trapped in the wings and diffuse a distance comparable to T . e also note the existence of a simple scaling law relating solutions for which the product (aro) is the same.