RADIATION TRAPPING WITH PARTIAL FREQUENCY REDISTRIBUTION - COMPARISONOF APPROXIMATIONS AND EXACT-SOLUTIONS

We treat radiation trapping with partial frequency redistribution. We solve the generalized Holstein equation by reducing it to an algebraic eigenvalue problem. In contrast to the complete frequency redistribut ion case, the eigensolutions depend not only on space but also on freq uency. We compare results obtained with exact angle-averaged frequency redistribution functions to various commonly used approximations. For pure Doppler broadening, the assumption of CFR gives less than 10% er ror. For Doppler plus natural broadening, the well-known Jefferies-Whi te approximation can lead to serious errors at high opacities.