Experimental demonstration of multiple-scattering suppression in quasielastic-light-scattering spectroscopy by homodyne coincidence techniques

Multiple-scattering artifacts are a not uncommon difficulty in applications of quasielastic-light-scattering spectroscopy (QELSS). An earlier proposal [G. Phillies, J. Chem. Phys. 74,260 (1981)] for a two-beam, two-detector light-scattering spectrometer, which is only sensitive to singly scattered photons, is subject here to an experimental test. The device is found to work essentially as predicted. The diffusion coefficient of 0.091-μm polystyrene spheres in water is concentration independent for solute volume fraction {}0.01. Multiple scattering does not have a significant effect on the QELSS spectrum of bovine serum albumin at a protein concentration of 20 wt.%.