Radiation Sources and Atom Reservoirs

In the discussion of the elementary steps of atomic spectroscopy, it is essential to distinguish between radiation sources and atom reservoirs . In the former, radiation is generated which is used for the spectroscopic measurement. The latter serve to produce free atoms (or ions) from the sample. The two devices may be separated, as is the case for atomic absorption (and also atomic fluorescence), or the atom reservoir may also be the radiation source, as for atomic emission. 

The volatilisation (vaporisation) and dissociation of the sample usually require highly energetic conditions to be as complete as possible. This is essential to maximise sensitivity while minimising matrix interferences at the same time. The effectiveness of volatilisation, atomisation, and excitation is dependent upon the supply of energy to the sample and is characterised by different spectroscopic temperatures. They represent an important diagnostic tool for the characterisation of atomisation conditions in the plasma  

Rotational temperature This is important for all processes where molecules or radicals are involved. It can be determined from the intensity distribution from the rotational lines in rotational—vibrational spectra. In most cases, diatomic molecules or radicals such as OH and CN are used as thermometric probes. 

Cas temperature This depends on the kinetic energy of the atoms and ions in the plasma. It can be determined from the Doppler peak broadening. This is however not completely straightforward, as the contributions of Doppler and temperature line broadening have to be separated by mathematical deconvolution. Together with the rotational temperature it is an indicator for the vaporisation and atomisation capability of a plasma. 

Electron temperature This is characteristic for the kinetic energy of the electrons. 

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