Two-laser induced selective infrared-visible fluorescence for thin film analysis

A laser technique has been developed to enhance its sensitivity for thin film analysis of mixtures. A c-w visible or uv laser was used to stimulate visible fluorescence from a thin fluorophor film, and a chopped low-power infrared laser was used to selectively excite characteristic infrared absorption bands in the sample. The resulting modulated visible fluorescence signal was monitored by an optical detection system. The technqiue has been applied to the quantitative determination of mixtures of coumarin 7, rubene, and rhodamine 6G; however, quantitative analysis has been impossible due to the difficulty in obtaining a uniform thin film. (BLM)