A laserhyphen;induced fluorescence (LIF) method for spatially resolved fragment detection and characterization in the radiation field of a photolysis laser is described. Measurements of the radiation field of a focused beam showed up highly inhomogeneous irradiation conditions, resulting in a strong local dependence of the laserhyphen;induced processes. The spatial resolution of the method is based on steppinghyphen;motorhyphen;controlled motion of the focusing lens of the photolysis laser versus the probe laser focused to a diameter (1/e2) of 58 mgr;m. This diameter corresponds to the spatial inhomogeneities of the quantities studied in this article. However, the monitored volume (5.3times;10minus;6cm3) also represents a compromise between acceptable S/N ratio and spectral resolution. The advantages and limits of this spatially resolved fluorescence (SRF) technique are discussed. Owing to its simplicity it can be readily implemented in existing laser photolysis equipment with conventional LIF detection. This method is currently being applied to the study of IR laser chemical reactions. A few examples illustrate the range of applicability of the method by providing information on the fluence dependence of product formation, on mass transport kinetics of molecular species in the context of heterogeneous laser processing, and on the internal energy distribution of the dissociation products. They show the much higher information content of SRF measurements as compared with conventional LIF measurements.
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