2000ApJ...531..411C

It is predicted that the Hα emission line at the early nebular epoch of Type II-P supernovae may display robust observational effects of radiation damping wings. Monte Carlo simulations demonstrate that the Hα line with the optical depth typical of the early nebular epoch acquires extended wings and redshift and becomes broader compared to the Sobolev approximation case. The strength of these effects may be used for constraining parameters of the line-emitting zone. The anomalous redshift, width, and red wing of the Hα emission in the supernova SN 1997D on day 150 are explained in terms of damping wings effects.