Sapphire pair-excitations

Figure 3.19. Absolute determination of 8 by in situ autocorrelation. Experiments were performed with a mode locked femtosecond Ti sapphire laser. A prism pair (PC) was used to compensate the group delay dispersion (GDD) of the microscope objective. A long-pass filter eliminates residual argon pump light and Ti sapphire fluorescence. After two sequential beam expanders (BE), the beam was approximately 25 mm in diameter, which was sufficient to overfill the back aperture (10-mm diameter) of the objective. A long-pass dichroic mirror (DC) with reflectivity separates fluorescence from excitation light. The incident power at the sample was measured by recollimating the transmitted beam onto a calibrated power meter. Fluorescence was detected by a photomultiplier tube and recorded as a function of the interferometer delay. (From Ref. [366] with permission of the Optical Society of America.)...

The reaction tube for the Na atom experiments consisted of a low-carbon stainless steel tube, enclosed by a pair of sapphire windows, with a side-arm reservoir for Na. It was in the center of an aluminum-block oven enclosed in high-porosity firebricks, and was maintained at 528 0.2 K. The reservoir temperature was controlled separately and was maintained 37 °C cooler than the reaction tube during experiments. The Na atoms were excited by the dye laser tuned to one of the Na doublet Hues at 589.1 or 589.7 nm. Typical signal averaged absorption curves obtained are shown in Fig. 2. 

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