Mixing Measurements Using Laser Induced Fluorescence

In this article, we present a novel method of quantitatively measuring mixing using laser induced fluorescence. This method is independent of flow and light sheet characteristics. The premise of this work is that molecular level mixing can be quantified through a scalar pH field in an aqueous solution. A two dimensional pH field can be determined in the solution by imaging the laser induced fluorescence of a pH sensitive dye which has been calibrated for fluorescence versus pH. This work differs from previous work in that the dye we selected exhibits dual band emission characteristics. By forming a ratio of the intensity image of each band's fluorescence, variations in dye concentration, laser light absorption and laser intensity are normalized out and a relationship between the ratio value and pH can be determined experimentally to within 0.1 a pH unit.