The net photon current is obtained from the exact transport solution for photon density in an infinite isotropic atmosphere. An analytical-numerical solution for the photon current is developed and presented graphically together with the diffusion theory current versus nondimensional distance.
JOHN F. BATTER, JR., "Transport Calculation of the Net Current of Photons in an Isotropically-Scattering Atmosphere," J. Opt. Soc. Am. 48, 371-373 (1958)