Measurement of triplet optical densities of organic compounds by means of CW laser excitation

Theodore G. Pavlopoulos

doi:10.1117/12.45142

1 April 1991 Measurement of triplet optical densities of organic compounds by means of CW laser excitation

Theodore G. Pavlopoulos

Proceedings Volume 1437, Applied Spectroscopy in Material Science; (1991) https://doi.org/10.1117/12.45142
Event: Optics, Electro-Optics, and Laser Applications in Science and Engineering, 1991, Los Angeles, CA, United States

Abstract

The application of cw lasers as powerful excitation sources for transient (triplet-) state spectroscopy is demonstrated. By focusing a cw laser beam on a sample with the aid of a lens, high triplet optical densities ODT((lambda) ) can be recorded. Using McClure's method, triplet extinction coefficients (epsilon) T((lambda) ) of many organic compounds are conveniently measured. To illustrate the method, we recorded (epsilon) T values on syn- (dimethoxyphosphinylmethyl,methyl) bimane. Exciting organic compounds with light causes various degrees of photodecomposition. We have developed a method to measure triplet optical densities ODT((lambda) ) in the presence of photodecomposition. The method is demonstrated on Coumarin 120. One records ODT((lambda) ) values as well as the accumulation of absorbing photoproducts as a function of time. Turning off the cw laser excitation, one records the accumulation of photoproducts only. Separating the two processes, one can determine how the triplet optical density declines as a function of time t. The decline curve can be expressed with an equation that is of second order in time. This equation allows one to extrapolate back to t equals 0 and recover ODT when there was no photodecomposition. Because the cw laser light is highly polarized, triplet-triplet (T-T) photoselection spectroscopy can be employed. The degree of polarization P of several syn- binanes was recorded, providing important insight on the polarization of T-T transitions. These data may be used to improve laser action properties of syn-bimanes by substitutions.

Citation Download Citation

Theodore G. Pavlopoulos "Measurement of triplet optical densities of organic compounds by means of CW laser excitation", Proc. SPIE 1437, Applied Spectroscopy in Material Science, (1 April 1991); https://doi.org/10.1117/12.45142

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