Using Slow Measurement Systems to Measure Fast Excited‐State Kinetics with Nonlinear Rate‐Competitive Optical Bleaching

Document Type

Article

Journal/Book Title

AIP Conference Proceedings: Photoacoustic and Photothermal Phenomena

Publication Date

1999

Editor

F. Scudieri and M. Bertolotti

Volume

463

First Page

14

Last Page

17

Abstract

The laser sources used in photothermal spectroscopy of homogeneous samples often have irradiances in excess of those required for singlet and triplet state optical bleaching of organic and biologically important molecules. These dynamic, nonlinear effects affect photothermal signal magnitudes in different ways, depending on the method used to detect the temperature change. In any case, signal magnitudes obtained at high irradiance and/or energy do not reflect the “small signal” absorbance, and apparatus calibration must take into account the change in effective absorption coefficient as a function of excitation irradiance and/or energy. This paper will present experimental methods for measuring nonlinear effects, methods and considerations for calibration for analytical measurement, and progress made towards interpretation of the nonlinear data in terms of the photophysics and excited state relaxation dynamics of the condensed phase species under study.

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