Transport of Fluorescence through Highly Scattering Media: Corrections to the Determination of Quantum Yields.

The equations for transport of fluorescence, generated within a highly scattering medium, are solved within the boundary conditions of the Kubelka and Munk treatment. Expressions are derived in closed form for fluorescence fluxes emanating from the front and back surfaces of a highly scattering infinite slab, whether or not fluorescence is absorbed within the sample. An "apparent" quantum yield, calculated from observed intensities of fluorescence and of back-scattered light from the front surface of the slab, can be corrected by these expressions to return the true quantum yield of fluorescence. Allowance for re-emission of reabsorbed fluorescence can be made, but may not be applicable in some experimental arrangements. Calculations performed on the fluorescence of rhodamine 101 suggest that in typical practical situations the correction factor may not be far from unity.