Quartz optical windows

The electrochemical cell used in our laboratory has been fully described elsewhere (5). The cell body is made of chemically inert Kel-F and the electrode is mounted on a piston so that its surface can be pushed to the optical window, to a spacing of the order of 1-3 microns, in order to minimize the signal from the bulk electrolyte. For Raman scattering spectroscopy the window is of flat fused quartz, and the exciting laser beam is incident at about 60°. The scattered light is collected off-normal, but the geometry is not critical for SERS due to the high sensitivity. Details on the SERS measurements in our laboratory have been reported previously (6,7). 

Pt acts like a neutral density filter through a wide wavelength range and can be used in the UV when the film is on quartz. Au has an optical window with maximum transmission at 540 nm. On quartz, Au can also be used in the UV when the conductivity is comparable to Pt. For the visible region, Au films with good transmission and with resistance as low as a few ohms per square can be prepared. Typical optical properties are shown in Figure 11.3 [55]. The electrochemical properties are similar to bulk Pt and Au, as seen in Figure 11.5 [74],... 

Wetted optical window Inert (sapphire, silica, quartz) Fragile (ZnSe, CaF2, KBr) Inert (sapphire, silica, quartz)... 

The MHS-1 uses a quartz optical cell, closed at both ends by quartz windows, which is heated up to 1000°C. The control module allows the choice of four programs which differ only in the timing of the purge and measurement cycles. The sample and reagent solution are mbced by a magnetic stirrer. 

Experimental Procedure. As source of ultraviolet light the Author used sparks between zinc electrodes, the hydrogen lamp (which gives a continuous spectrum), or mercury lamps of differing model and power, fed by alternating or by direct current all the mercury lamps emit an arc spectrum. The spectra from these sources were determined by a spectrograph with quartz optics or a diffraction spectrograph with a fluorite window. ... 

Fig. 1. Schematic representation of vacuum furnace closed-cycle helium refrigeration system used for metal vapor microsolution optical spectroscopy, as well as conventional metal vapor-matrix isolation experiments. (A) NaCl or Suprasil optical window, horizontal configuration (B) stainless steel vacuum shroud (C) NaCl or Suprasil optical viewing ports (D) cajon-rubber septum, liquid or solution injection port (E) gas deposition ports (F) vacuum furnace quartz crystal microbalance assembly. With the optical window in a fixed horizontal configuration, liquid or solution sample injection onto the window at any desired temperature in the range 12-300 K is performed in position 1A, metal deposition is conducted in position IB, and optical spectra are recorded in position 1C see Procedure).

For UV diffuse reflectance measurements CVD powder was placed in a high vacuum tight quartz cell with optical windows made of Suprasil. Thermal activation, as well as adsorption and desorption steps were performed by connecting the cell to a conventional vacuum line that also guarantees pressures less than 10" mbar. The UV spectra were acquired using a Perkin Elmer Lambda 15 spectrophotometer equipped with an integrating sphere. BaS04 powder was used as a reference. 

The most common cell for solutions is a 1 cm rectangular quartz or glass cuvet with four optical windows. Eor extremely small volumes, fiber optic probes, microvolume cells, and flow cells are available. Gas cells, and special sample compartments for solid samples are commercially available. 

The molecular absorption phenomenon can only be accurately measured provided that the ratio of transmitted intensity, 7, of the UV radiation to that of the incident intensity, /q, is due to the presence of the dissolved solute and not to scattering of the incident beam. If the optical windows (see below) absorb UV radiation, then the absorbance which is related to the logarithm of the ratio ///q would cause an increase in sample absorbance hence, this would lead to an erroneous result. The student will encounter two types of optical window material. One consists of glass and is said to have a UV cutoff (UV wavelengths below this would absorb) of 300 nm (near UV) and the other consists of quartz with a UV cutoff of 190 nm. The rectangular cuvette is depicted as follows ... 

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