Figure ,D shows the UV/Vis-DOSY spectrum of the two-component dye solution obtained in this way. In the DOSY spectrum, the total absorption spectrum (shown in the top panel of Fig. ) is separated into two sets of peaks at different y-coordinates (=diffusion coefficients), each corresponding to one of the dyes present in the solution, and the value of the diffusion coefficient provides information on the size. Our experimental values for the diffusion coefficients are somewhat lower (about 35%) than the previously reported values due to the presence of PEG (polyethylene glycol) which we use to ensure laminar flow. In the case of unknown molecules in a mixed solution, the value of the diffusion coefficient can be used to obtain an estimate of the size of the compounds, and the UV/Vis spectrum associated with a diffusion constant provides information on the electronic structure of the molecule or particle. If the extinction coefficients of the components are known, then the A i (λ) spectra (horizontal slices of the DOSY spectrum) can be used to determine their concentrations in the sample solution. In this example, the spectrum contains isolated peaks for each component (so that the diffusion coefficient can be determined from analyzing the time-dependence at the corresponding wavelengths), but this is not a necessary requirement, as we will see next.