Quantitative vapour-liquid visualization using laser-induced exciplex fluorescence

We describe an optical technique for quantitative evaluation of the concent rations of coexisting vapour and liquid phases in a spray. A laser-induced exciplex fluorescence visualization system allows time-resolved two-dimensi onal fluorescence images of vapour and liquid distributions to be acquired simultaneously using two-colour emission. The method is based on the excipl ex formers DRA (N, N-dimethylaniline) and 1, 4, 6-TMN (trimethylnaphthalene ) in a non-polar solvent. We report here methods for quantitatively calibra ting the liquid and vapour phases of a solution containing 90% isooctane., 5% DMA and 5% 1, 4, 6-TMN. The evaluation of fluorescence intensities yield s quantitative two-dimensional concentration maps of liquid and vapour phas es. This technique is expected to find applications in studying mixture for mation in diesel or spark ignition engines with spectrally well-separated f luorescence images obtained from the monomer and exciplex constituents diss olved in a fuel.