Ionization temperature, atomic spectroscopy

In atomic spectroscopy, absorption, emission, or fluorescence from gaseous atoms is measured. Liquids may be atomized by a plasma, a furnace, or a flame. Flame temperatures are usually in the range 2 300-3 400 K. The choice of fuel and oxidant determines the temperature of the flame and affects the extent of spectral, chemical, or ionization interference that will be encountered. Temperature instability affects atomization in atomic absorption and has an even larger effect on atomic emission, because the excited-state popula-... 

Excessive ionization can reduce the atomic spectroscopy signal from the neutral atom, although accurate quantitation can still be conducted as long as the degree of ionization remains constant for all samples and standards. In some high-temperature sources, ionization is sufficiently large for ions to be... 

The atomization/ionization in ICP spectroscopy is accomplished via the high-temperature plasma source. The plasma is obtained by applying a high-frequency magnetic field to an ionized argon gas stream in the ICP torch device (Fig. 5). 

To examine a sample by inductively coupled plasma mass spectrometry (ICP/MS) or inductively coupled plasma atomic-emission spectroscopy (ICP/AES) the sample must be transported into the flame of a plasma torch. Once in the flame, sample molecules are literally ripped apart to form ions of their constituent elements. These fragmentation and ionization processes are described in Chapters 6 and 14. To introduce samples into the center of the (plasma) flame, they must be transported there as gases, as finely dispersed droplets of a solution, or as fine particulate matter. The various methods of sample introduction are described here in three parts — A, B, and C Chapters 15, 16, and 17 — to cover gases, solutions (liquids), and solids. Some types of sample inlets are multipurpose and can be used with gases and liquids or with liquids and solids, but others have been designed specifically for only one kind of analysis. However, the principles governing the operation of inlet systems fall into a small number of categories. This chapter discusses specifically substances that are normally liquids at ambient temperatures. This sort of inlet is the commonest in analytical work. 

Atomic absorption spectroscopy is highly specific and there are very few cases of interference due to the similar emission lines from different elements. General interference effects, such as anionic and matrix effects, are very similar to those described under flame emission photometry and generally result in reduced absorbance values being recorded. Similarly, the use of high temperature flames may result in reduced absorbance values due to ionization effects. However, ionization of a test element can often be minimized by incorporating an excess of an ionizable metal, e.g. potassium or caesium, in both the standards and samples. This will suppress the ionization of the test element and in effect increase the number of test atoms in the flame. 

The monograph is dedicated to those who are interested in the theory of many-electron atoms and ions, including very highly ionized ones, in the fundamental and applied spectroscopy of both laboratory (laser produced, thermonuclear, etc.) and non-atmospheric astrophysical low-and high-temperature plasma. To some extent it may serve as a reference book and textbook for physicists and astrophysicists. 

In 677-SiC, B replaces a Si atom and its ionization energies in the three non-equivalent sites measured by admittance spectroscopy are 0.27, 0.31, and 0.38 eV [56], In undoped and boron-doped p-type 6H-SiC samples, a photoionization spectrum with a temperature-dependent threshold between 0.5 and 0.7eV, and a maximum at 1.75 eV has been reported [83]. The difference between the threshold energy and the electrically-measured ionization energy of B (0.3-0.4eV) is attributed to lattice relaxation. This photoionization spectrum is correlated with the observation near LHeT of three narrow absorption lines at 2.824, 2.863, and 2.890 eV tentatively attributed to excitons bound to neutral B at the three possible sites in 6H-SiC. 

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