APPLICATION OF MIRAGE SPECTROSCOPY TO THE IN SITU ANALYSIS OF PHOTODECOMPOSITION PROCESSES.

Photothermal or mirage spectra are obtained by observing the generation of a thermal gradient in the near electrode region of the electrolyte as a function of the frequency of light impinging on the electrode. Thermal gradients as small as 10** minus **5 degree C are easily monitored by noting the spatial deflection of a low intensity collimated He-Ne laser beam which is passed parallel to the electrode surface. Hence by varying the frequency of light illuminating the electrode and monitoring probe beam deflection, using locks in amplification techniques to remove external thermal interferences, one may obtain optical spectra of an electrode surface under operational electrochemical conditions. The electrode employed need not have any special optical properties (i. e. single crystal, optically polished, optically transparent, etc. ). Such a technique offers opportunities in the study of decomposition or overlayer formation processes occurring at illuminated semiconductor-liquid junctions.