Laser measurement of the spectral extinction coefficients of fluorescent, highly absorbing liquids.

A conceptual method has been developed to deduce rapidly the spectral extinction coefficient of fluorescent, highly absorbing liquids such as crude or refined petroleum oils. The technique has the advantage of only requiring one laser wavelength and a single experimental assembly and execution for any specific fluorescent liquid. The liquid is inserted into a very thin wedge-shaped cavity for stimulation by a laser from one side and fluorescence measurement on the other side by a monochromator system. For each arbitrarily chosen extinction wavelength the wedge is driven slowly to increasing thicknesses until the fluorescence extinguishes. The fluorescence as a function of wedge thickness allows the determination of the extinction coefficient using an included theoretical model. When the monochromator is set to the laser emission wavelength, the extinction coefficient is determined with the usual on-wavelength signal extinction procedure. For all other wavelengths, the technique is limited to those spectral regions possessing fluorescence.