Calcium fluoride windows

Calcium fluoride is insoluble in water and is transparent to light. Because of these properties, calcium fluoride is sometimes used to make windows for optical devices. Design a synthesis of 1.0 kg of CaF2. ... 

Infrared detectors are similar in construction to those used in UV detection. The main difference is that the sample cell windows are constructed of sodium chloride, potassium bromide, or calcium fluoride. A limitation of this type of detector is caused by the low transparency of many useful solvents (Skoog et al., 1998). Recent changes to interface systems that use spraying to induce rapid evaporation of the solvent provide good sensitivity and enhanced spectral quality (LaCourse, 2000). 

According to the specific task, different materials are used for the windows. Typical materials are sapphire, calcium fluoride, zinc selenide, diamond, and normal quartz. The selection of the materials depends on the pressure and, for spectroscpic investigations, also on the wavelength corresponding to the bonds of the species to be analysed. 

The opposed anvil cell consists of two optical anvils and a gasket, located between the parallel faces of the two opposing anvils. Samples are placed in the hole of the gasket and are pressurized when the opposed anvils are pushed towards each other. The most common material for anvils is diamond. For mid and far infrared spectra, type Ila diamonds are used, while low-fluorescent type la diamonds are used for Raman spectroscopic measurements [5]. We have also devised a glass anvil cell for Raman spectroscopic measurements [6], and a calcium fluoride anvil cell for infrared spectroscopic measurements [7] with attainable working pressures of 13 and 6 kbar, respectively. Diagrams, for the interested reader, of the window and opposed anvil cells can be found in reference 1. 

The protein concentration used in the mid-IR measurements was about 15 mM in heme. The protein solution was centrifuged at 5000 g for 15 minutes prior to being anaerobically transferred into a gas-tight 0.1-mm-path-length sample cell. The sample cell consisted of two 2-mm-thick calcium fluoride windows separated by a 0.1 mm spacer. The sample cell was mounted in a refrigerated enclosure, chilled to 10°C, and rotated fast enough to ensure that each photolysis pulse illuminated a fresh volume within the protein sample. 

The evacuated spectrometer (p < 10 mbar) was attached to a small UHV chamber using calcium-fluoride windows. The small UHV chamber was part of a larger surface analysis system. The polymer films were produced in the vacuum system by vapor deposition and analyzed in ultra-high vacuum without exposure to air. 

The near infrared cell is also Monel. The body of the cell is 2.0 cm. in diameter and 7.5 cm. long. The windows are calcium fluoride and are sealed to the nickel body with Halocarbon wax 8-00. The valve is a Hoke 323 stainless steel valve. 

Complete descriptions of the particle beam, its operation, its experimental setup, and its utility in protein structural studies have been previously described. (8, 12). Relevant PB dimensions include a 25 pm diameter fused silica capillary for production of the aerosol spray, a 22 cm length desolvation chamber to remove solvent, a single stage momentum separator, and a nozzle-substrate distance of 5 mm. Particle beam deposits ranged in size from 20 pm to 100 pm in diameter, and averaged approximately 50 pm. Deposit were made onto a water insoluble calcium fluoride (CaFj) window (25 mm dia. x 2 mm) from International Crystal Laboratories (Garfield, NJ). 

Infrared, like the UV and visible regions of the spectrum, provides a useful method for detecting solutes in liquid streams. The detector uses the principle of attenuated total reflectance, with a single beam spectrometer being used in conjunction with a tow volume flow cell. The cell is equipped with sodium chloride, calcium fluoride or zinc selenide windows and can be heated to temperatures greater than 100°C. The detector can... 

Figure 5.1 Disassembled view of the spectroelectrochemical cell. (1) Tightening brass cap (threaded inside). (2) Brass ring required to tighten the cell. (3) Working electrode (brass rod with platinum soldered to the base). (4) Auxiliary electrode platinum wire with the tip made flush to the teflon base of the cell. (5) Pseudoreference electrode silver wire, also made flush to the teflon. (6,7) Luer-lock-type injection ports. (8) Cell body, top part aluminium, lower part teflon. (All three electrodes and both filling ports are press fitted into the cell body, so that they can be replaced if needed.) (9) Teflon spacer, determines the pathlength of the cell and masks the reference and counter electrodes from the incident beam. (10) Calcium fluoride window (Wilmad, standard 38.5 x 19.5 x 4mm). (11) Rubber gasket. (12) Hollow brass cell body with threaded inlet and outlet ports (Swagelock) for connection to circulating bath. (13) Two-mirror reflectance accessory (Thermo-SpectraTech FT-30). (14,15) Mirrors.

Calcium fluoride occurs naturally as the mineral fluorspar, and is commercially important as the raw material for the manufacture of HF (equation 11.6) and F2 (see Section 16.2). Smaller amounts of Cap2 are used as a flux in the steel industry, for welding electrode coatings, and in glass manufacture prisms and cell windows made from Cap2 are used in spectrophotometers. 

The apparatus in Fig. 1 may be easily modified for incident zone experiments by replacing the end plug with a suitable length of pipe. The test section consists largely of rectangular tubing in order that the planar calcium fluoride windows may be mounted on flat surfaces. A smooth transition from the circular cross-section of the driver to the rectangular cross-section of the test section is accomplished in the expansion section. 

Infrared Absorption Detectors. Two types of infrared detectors have been offered commercially. The first is a filter instrument similar in design to that shown in Figure 16-13. The second, and more sophisticated, type of infrared detector is based on Fourier transform instruments similar to those discussed in Section I6B-1. Several of the manufacturers of Fourier transform infrared (FTIR) instruments offer accessories that permit their use as HPLC detectors. Infrared detector cells are similar in construction to those used with ultraviolet radiation except that windows arc constructed of sodium chloride or calcium fluoride. Cell path lengths range from 0.2 to 1.0 mm and volumes from 1.5 to 10 pL. 

Klein CA (2006) Calcium fluoride windows for high-energy ehemical lasers. J Appl Phys 100 083101... 

Vacuum spectrometers require windows over the entrance and exit slits to maintain the vacuum. They are usually made of lithium fluoride or calcium fluoride. If photographic plates are used to record spectra, special arrangements are required to either place the plate inside the monochromator case or provide a system to remove the plate and replace it without breaking the vacuum. Both arrangements are used commercially. 

Temperature controlled IR measurements of liquid samples (solution in CCU) were measured in a Wilmad temperature-controlled cell mount with calcium fluoride windows. The sample was surrounded by a heat sink that was filled with a heat transfer fluid (antifreeze), which was regulated by a Noah Precision temperature controller. The cell mount was sealed in the nitrogen-flushed IR compartment. 

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