Optical cells for vibrational spectroscopy of fluids at high pressures and temperatures

2 Optical cells for vibrational spectroscopy of fluids at high pressures and temperatures 

Even if the focus is exclusively on optical cells, it is impossible to review the large number of published experimental arrangements in a chapter of limited size. Since the field has already been treated by Sherman and Stadtmuller (1987), this text is only concerned with optical cells for vibrational spectroscopic studies (IR, NIR, Raman) of fluid phases under conditions involving high pressure and high temperature up to a maximum of about 650 °C and 7 kbar. This is the area of the authors greatest personal experience (Buback, 1981 Buback et al., 1987). 

One of the windows (1) is sealed to a fixed steel plug (5). The second window (2) is attached to a movable piston (12), which is sealed to a packing (7) by means of a screw (10). The screw (11), between (10) and the piston (12), has different threads on the inner and the outer diameter. In the special cell shown in Fig. 6.7-6, which may be operated up to 2.5 kbar and 200 °C, the pitch of the screws is 1.50 mm and 1.25 mm. Due to this difference, the turning screw (11), while (10) and (12) are mounted in counter-rotatory direction (by auxiliary equipment not shown in Fig. 6.7-6), moves 

Following the same principles as those which govern the designing of cells for absorption experiments, Raman cells for high-pressure, high- temperature studies have also been constructed by Lindner and Franck (see Tddheide, 1972). A Raman cell for use up to 7 kbar and 250 °C (Eckel et al., 1981) is shown in Fig. 6.7-8. 

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