Noble gas analysis

Reynolds, J. H. (1956) High-sensitivity mass spectrometer for noble gas analysis. Rev. Scientific Instruments, 27, 928-34. 

The determination of noble gases in water can be divided into three successive analytical steps (1) noble gas extraction from the water, (2) purification and separation of the extracted noble gases, and (3) quantitative (mass spectrometric) analysis. For extended discussions of methods for noble gas analysis in waters (and other terrestrial fluids) the readers are referred to Clarke et al. (1976), Rudolph (1981), Bayer et al. (1989), Stute (1989), Groning (1994), Ludin et al. (1997), and Beyerle et al. (2000a). 

Electron impact (El) ionization is useful for elements that are either volatile or form volatile compounds. Typical ionization efficiencies are in the range of 0.1 to 1 percent. Suitable elements include noble gases and light elements such as C, N, O. Other elements include those that form volatile compounds (e.g., uranium in the form of UFg). Except for specialized applications (e.g., noble gas analysis), El is no longer widely used for elemental and isotopic analysis. 

The noble gas analysis system is called ARSA, the Automated Radioxenon Sampler/Analyser. This uses two different detection techniques, P-y coincidence or high-resolution gamma spectrometry. The nuchdes sought are i3imxr, i33xe, i33 Xe and Xe, with a limit of measurement of 1 mBqm for Xe. The measurement scheme is as follows ... 

Surface composition analysis by LEIS is based on the use of noble gas ions as projectiles, making use of the superb surface sensitivity of LEIS under these conditions. A consequence of this surface sensitivity is that the LEIS energy spectrum consists of lines, one per element, if the masses differ sufficiently. The lines are narrow, because inelastic energy losses play a minor role here. Thus, the information on the atomic species present is deduced from the energy of the back-scattered ions, which can be converted to the mass of the scattering center. (Eig. 3.55 [3.141]). In Eig. 3.55 it is shown that the mass range, where LEIS is sensitive, depends on the projectile mass. 

The atom probe field-ion microscope (APFIM) and its subsequent developments, the position-sensitive atom probe (POSAP) and the pulsed laser atom probe (PLAP), have the ultimate sensitivity in compositional analysis (i.e. single atoms). FIM is purely an imaging technique in which the specimen in the form of a needle with a very fine point (radius 10-100 nm) is at low temperature (liquid nitrogen or helium) and surrounded by a noble gas (He, Ne, or Ar) at 10 -10 Pa. A fluorescent screen or a... 

In 1962 the report, TID-14844 was published presenting analysis and assumptions coneeming the behavior of containment (essentially Hazard State 2). The TID report postulated the release of all of the noble gas, 50% of the iodine, and 1% of the radioactive solids to the containment. In addition, TBD-14844 provided assumptions for containment leakage (the TMI-2 containment is intact) and for atmo.spheric transport of the fission products. These results form the basis for Regulatory... 

Another very important technique for fundamental consideration of multicomponent systems is low energy ion scattering (LEIS) [Taglauer and Heiland, 1980 Brongersma et al., 2007]. This is a unique tool in surface analysis, since it provides the ability to define the atomic composition of the topmost surface layer under UHV conditions. The signal does not interfere with the subsurface atomic layers, and therefore the results of LEIS analysis represent exclusively the response from the outer surface. In LEIS, a surface is used as a target that scatters a noble gas ion beam (He, Ne, ... 

Two important substances have so far not been found on Titan the noble gas argon and water. The analysis of the results of the successful Cassini mission may soon shed light on this mystery. 

For many elements, the atomization efficiency (the ratio of the number of atoms to the total number of analyte species, atoms, ions and molecules in the flame) is 1, but for others it is less than 1, even for the nitrous oxide-acetylene flame (for example, it is very low for the lanthanides). Even when atoms have been formed they may be lost by compound formation and ionization. The latter is a particular problem for elements on the left of the Periodic Table (e.g. Na Na + e the ion has a noble gas configuration, is difficult to excite and so is lost analytically). Ionization increases exponentially with increase in temperature, such that it must be considered a problem for the alkali, alkaline earth, and rare earth elements and also some others (e g. Al, Ga, In, Sc, Ti, Tl) in the nitrous oxide-acetylene flame. Thus, we observe some self-suppression of ionization at higher concentrations. For trace analysis, an ionization suppressor or buffer consisting of a large excess of an easily ionizable element (e g. caesium or potassium) is added. The excess caesium ionizes in the flame, suppressing ionization (e g. of sodium) by a simple, mass action effect ... 

Akeypart in the analysis and proposal was electron accountancy - on the basis of the usual propensity for the adoption of a noble gas outer shell configuration - and all of the proposed intermediates have 16- or 18-electron configurations except the metallocyclobutane (26) in pathway II which has 14. On this basis, one might expect that pathway I, the non-dissociative pathway, would predominate over pathway II. In the presence of a large excess of Cy3P, which was used only to simplify the kinetic analysis, this is clearly the case. However, under the... 

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