Laser‐Excited Photothermal Lens Spectrometry in a Low‐Volume Cylindrical Sample Cell

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Israel Journal of Chemistry

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A new apparatus for performing laser-excited photothermal lens spectroscopy is described. The apparatus uses a sub-microliter cylindrical sample cell, chopped laser excitation, and a continuous probe laser to perform photothermal lens spectrometry. The sample is irradiated with a constant irradiance beam, and the photothermal lens forms due to thermal diffusion through the sample cell walls. Solutions for the thermal diffusion equations predict a parabolic temperature change under continuous irradiation. Experimental results are obtained for organic and inorganic complexes in ethanol solution and compared to those obtained using a standard sample cell. Results for dicyclopentadienyl iron solutions excited with 10mW 514.5 nm Ar+ laser radiation show that the cylindrical sample cell signal is 32% of that obtained using the standard sample cell. This ratio is in reasonable agreement with that expected based on thermal diffusion models. Results obtained for ruthenium tris-bipyridyl chloride and perchlorate salts are not stable with respect to irradiation time. The latter results suggest that a significant amount of ruthenium tris-bipyridyl complex is photolyzed with the mild irradiation conditions used in these experiments.

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