Direct method for numerical study of radiation trapping

A direct method for numerical investigation of radiation trapping within th e framework of the Holstein-Biberman equation is put forward; The method is based on time propagation of the initial distribution of excited atoms wit h the split-propagation technique. Some results obtained for circular and e lliptic geometries of the gas cells are given in comparison with the data o f previous calculations. The present method allows one to investigate vario us transfer phenomena occurring in an arbitrary (three-dimensional) convex spatial region and driven by the external conditions with arbitrary time de pendences.