Tungsten ionization energy

For vanadium and chromium the first ionization energies are much lower than the first ionization energies of phosphorus and sulphur, respectively. This explains the high heats of formation of VC13 and CrCl3. In uranium, the tetravalent state is more stable than that in tungsten because uranium as an actinide has a different electron configuration. 

The loss of free atoms in the atomizer is also a function of the chemistry of the sample. If the oxide of the analyte element is readily formed, the free atoms will form oxides in the flame and the population of free atoms will simultaneously decrease. This is the case with elements such as chromium, molybdenum, tungsten, and vanadium. On the other hand, some metal atoms are stable in the flame and the free atoms exist for a prolonged period. This is particularly so with the noble metals platinum, gold, and silver. Adjusting the fuel/oxidant ratio can change the flame chemistry and atom distribution in the flame as shown in Fig. 6.17(b). Atoms with small ionization energies will ionize readily at high temperatures (and even at moderate temperatures). In an air-acetylene flame, it can be shown that moderate concentrations of potassium are about 50% ionized, for example. Ions do not absorb atomic lines. 

Figure 51.2 ) Generation of a plasma and its use in plasma coating. An arc passes from the tungsten cathode to the water-cooled copper anode. Argon is forced through the arc and is ionized. On recombination beyond the outlet, the ionization energy is returned and the tem-...

In 1923, Kingdom and Langmuir [1] first observed SI (Fig. 1). This phenomenon consisted of desorption of cesium (Cs) atoms in the form of positive ions from the surface of a heated tungsten (W) filament. Subsequently, numerous studies of positive-ion SI have been conducted, since this effect opens interesting possibilities for analysis of chemical species with low ionization energy (IE), for ion production, and for the detection of molecular and atomic beams. After the Saha-Langmuir equation [2] was established and well defined, further studies have [3,4] been directed to the atoms of virtually all elements, which have a low ionization energy. Especially, SI was studied for suitability as a source of ions for precise isotope-ratio measurements [5] and isotope-dilution techniques. It is apparent, however, that its use has, until recently, been restricted to metals. 

The electrons are produced by heating a metallic filament (usually tungsten or rhenium) and accelerated by a voltage of 70 V that provides them a kinetic energy of 70 eV. Disposing of an international standard for the ionization energy allows a comparison of mass spectra recorded on different types of devices. Another benefit is access to databases that classify many thousands of mass spectra, which eliminates the need to interpret the spectra to identify the analytes. The databases are... 

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