A Computer Simulation of Phase-Shift Measurements of the Quenching and Trapping of Resonance Radiation at Large Optical Depths.

摘要

Numerical calculations of the build-up and decay of fluorescence have been made for a model system in which the rate of internal radiative transfer to a point is governed by the average concentration of excited species in the immediate neighbourhood of that point. This corresponds to the limit of very large optical depth. The concentration of excited species has been evaluated as a function of time at each point on a cubical grid, for grids having 5, 9, 13, 17, or 21 equally-spaced points along each axis. The phase and amplitude of the fluorescence signal have been calculated for various quencher concentrations, modulation frequencies, and points of observation. The radiation trapping time characteristic of the quenching of steady-state fluorescence differed from that calculated from the phase delay between the fundamental components of exciting radiation and fluorescence.