Analysis Residual gas

For intermediate temperatures from 400-1000°C (Fig. 11), the volatilization of carbon atoms by energetic plasma ions becomes important. As seen in the upper curve of Fig. 11, helium does not have a chemical erosion component of its sputter yield. In currently operating machines the two major contributors to chemical erosion are the ions of hydrogen and oxygen. The typical chemical species which evolve from the surface, as measured by residual gas analysis [37] and optical emission [38], are hydrocarbons, carbon monoxide, and carbon dioxide. 

O Hanlon, J. F., 1980. A Users Guide to Vacuum Technology. Wiley, New York. This hook is oriented somewhat to semiconductor and optics applications. II has very useful sections on residual gas analysis. 

An interesting result was the appearance of F+ in the residual gas analysis when the electron beam in AES was placed on the sample, suggesting easy desorption and a very unstable surface. In fact, when electron beam currents were not minimized, the fluorine frequently was desorbed completely, and did not appear in the Auger spectrum. 

A UHV chamber for LEED studies is evacuated to ultra-high vacuum with a combination of pumps consisting of a turbomolecular pump (backed with an oil-sealed rotary vane pump) and a titanium sublimation pump (TSP). When the chamber is evacuated by both pumps, a total pressure of 4 x 10 9mbar is achieved and residual gas analysis shows that this consists of 50% Ar + 50% H2. 

The identification and quantification (partial pressure measurement) of the gaseous components in vacuum systems is of increasing importance in vacuum technology. This is achieved by the widely applied method of residual gas analysis. The simple theory of this is stated and relevant examples illustrate the application. 

Measurement of total pressure is insufficient for the characterisation of vacuum systems. Detailed information (system cleanliness, presence of leaks, etc.) can only be obtained by the identification of components present in the gas phase by means of residual gas analysis. Having established gas composition, however, the determination of partial pressures is relatively straightforward. 

Explain the presentation of the residual gas analysis data in Table 5.2. Calculate the fragmentation factors (FF) associated with the given peaks. 

Residual gas analysis with quadrupole mass spectrometers is being used increasingly in many applications for characterisation and problem diagnosis. Typical data were shown (Examples 5.16 and 5.17) and the manipulation of such data to yield partial pressures performed in Examples 5.18 and 5.19. 

A major reason why XAFS spectroscopy has become a critically useful probe of catalyst structure is the fact that it is easily adapted to characterization of samples in reactive atmospheres. The X-ray photons are sufficiently penetrating that absorption by the reaction medium is minimal. Moreover, the use of X-ray- transparent windows on the catalytic reaction cell allows the structure of the catalyst to be probed at reaction temperature and pressure. For example, the catalyst may be in a reaction cell, with feed flowing over it, and normal online analytical tools (gas chromatography, residual gas analysis, Fourier transform (FT) infrared spectroscopy, or others) can be used to monitor the products while at the same time the interaction of the X-rays with the catalyst can be used to determine critical information about the electronic and geometric structure of the catalyst. 

Because discharge lamps are invariably windowless and differentially pumped, the partial pressure of helium in the vacuum chamber is likely to rise considerably during the experiment. A mass spectrometer for residual gas analysis is therefore absolutely necessary to check the purity of the helium. 

The decomposition of Mg(BH4)2 has been extensively studied using in situ XRD techniques coupled with residual gas analysis (RGA) measurements of the gas release. They report that the borohydride decomposed starting at 300°C, releasing 9 wt% H2 by 350°C. No ordered phase was detected by the XRD between these two temperatures, indicative of an amorphous phase or phases. Above 350°C, MgH2 apparently recrystallized and was detected by the XRD. This phase subsequently released the additional hydrogen as the temperature was increased further. Initial attempts to recharge the spent material indicated that only the Mg rehydrided to form MgH2. 

Residual moisture is the low level of water, usually in the range of less than 1-3% (wt/wt), remaining in a freeze-dried product after the freeze-drying (vacuum sublimation) process [1-5] is complete. Nail [6] has described in-process methods to monitor the endpoint of freeze-drying using residual gas analysis, pressure rise, comparative pressure measurement, and product temperature measurement. Roy and Pikal [7] used an electronic moisture sensor inside the lyophilization chamber. Residual moisture [8] content is important in the final freeze-dried product because it affects the potency of the product, its long-term stability, and the official shelf life of the product. 

Ferran, R.J. Boumsellek, S. High-pressure effects in miniature arrays of quadrupole analyzers for residual gas analysis from 10-9 to 10-2T orr. J. Vac. Sci. Technol. A 1996,14,1258-1265. 

So, the systematic bibliography presented in this review, had led us to present the results not by way of formulae, curves and tables which most of the time would have been valid for a special sample only, but by the much better possible comparison of well defined properties. This choice has been determined by the complexity of the results. The treatment of one magnetic property can lead to the report of many curves, the presentation of many large tables, or finally to the exposition of many different models (formulae, hypotheses,...) such that a clear classification will be difficult, if not impossible. Such a situation comes from the fact that numerous papers do not give precisely all the many experimental parameters chemical analysis of the starting bulk material, residual gas analysis in the vacuum, cleanness of the substrates, thickness and composition of the films, presence of a possible sublayer at the film-substrate or at the film-air interfaces. X-ray and electron diffraction patterns, Likewise the exact pos-... 

Residual-gas analysis (RGA), a mass-spectrometric method, is the most accurate method for measuring moisture and other low-molecular-weight volatile compounds released from polymeric materials. Interpretation of RGA data has at times proven difficult since small differences in the processing of samples intended to be identical resulted in major differences in the results and analyses of the same circuits by different laboratories. Most of these differences have been resolved by using laboratories that are certified by government agencies, such as Defense Supply Center at Columbus (DSCC), using their own standards. 

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