Visible radiation, electronic energy level

The principle of ICP-AES is that atoms (or sometimes ions) are thermally excited, in a plasma torch, to higher energy levels, these atoms or ions then relax back to lower electronic energy levels by emitting radiation in the UV-visible region. The emitted radiation is detected and used to determine which elements are present, and their concentration. Analysis of organometallic and inorganic additives, based on the ICP-AES determination of specific metal ions, is routinely undertaken. 

The absorption of ultraviolet and/or visible radiation by polymers leads to transition among the electronic energy levels of the macromolecules, and as a result of this a typical electronic absorption spectrum is obtained (Fig. 10.53). 

When the atoms of samples are excited to higher electronic energy levels in flames they emit radiation in the visible and UV regions of the electromagnetic spectrum. Emission intensities may be measured to analyze for metals, especially alkali and alkaline earth elements. 

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