PHOTOACOUSTIC DETERMINATION OF FLUORESCENCE QUANTUM YIELD

FLUORESCENCE METHODS ARE USED THROUGHOUT A VARIETY OF FIELDS INCLUDING BIOTECHNOLOGY, MICROSCOPY, IMMUNOLOGY, BIOLOGY, CHEMISTRY, PHOTOCHEMISTRY, AND PHOTOPHYSICS. MANY FLUORESCENCE TECHNIQUES EMPLOY CHANGES IN FLUORESCENCE INTENSITY OF CHROMOPHORES IN RESPONSE TO THEIR MOLECULAR ENVIRONMENT. THE GOAL IS TO CORRELATE FLUORESCENCE INTENSITY (AN ARBITRARY VALUE) WITH FLUORESCENCE QUANTUM YIELD (A FUNDAMENTAL PHOTOPHYSICAL PARAMETER, BUT ONE THAT IS DIFFICULT TO MEASURE). THE OBJECTIVE IS TO DETERMINE THE FEASIBILITY OF USING A PULSED-LASER PHOTOACOUSTIC METHOD COMBINED WITH FLUORESCENCE DETECTION TO DETERMINE FLUORESCENCE QUANTUM YIELDS ACCURATELY. SUCH A DETERMINATION SHOULD BE POSSIBLE WITH RELATIVELY INEXPENSIVE INSTRUMENTATION, AND SUFFICIENT AUTOMATION TO MAKE QUANTUM YIELD DETERMINATIONS RAPID AND EASY TO PERFORM. A PULSED-LASER BEAM EXCITES A SOLUTION OF MOLECULES, A LIGHT DETECTOR MEASURES FLUORESCENCE, AND A PIEZOELECTRIC TRANSDUCER IS USED TO DETERMINE THE AMPLITUDE OF A COMPRESSIVE SOUND WAVE RESULTING FROM HEAT DEPOSITED IN THE SOLUTION. YIELDS OF TRIPLET STATES WILL BE DISTINGUISHED BECAUSE SUCH STATE ARE LONG-LIVED. TO SUPPORT THE AUTOMATION OF THIS TECHNIQUE, METHODS FOR DETERMINING THE AVERAGE EMITTED PHOTON ENERGY WITHOUT RESORTING TO A COMPLETE FLUORESCENCE SPECTRAL MEASUREMENT ARE BEING STUDIED.