Atoms and Atomic Spectroscopy

Each element has a unique set of permitted electronic energy levels because of its unique electronic structure. The wavelengths of light absorbed or emitted by atoms of an element are characteristic of that element. The absorption of radiant energy by atoms forms the basis of atomic absorption spectrometry (AAS) discussed in Chapter 6. The absorption of energy and the subsequent emission of radiant energy by excited atoms form the basis of atomic anission spectroscopy and atomic fluorescence spectroscopy, discussed in Chapter 7. 

It is possible for atoms to absorb higher-energy radialion, in the X-ray region such absorption may result in the inner shell (core) electrons being promoted to an excited state, with the subsequent anis-sion of X-ray radiation. This process forms the basics for quaUtalive and quantitative elemental analysis by X-ray fluorescence (XRF) spectroscopy, as well as other X-ray techniques, discussed in Chapter 8. 

UV/VIS region for short. The energy level diagrams for all elements have been determined, and tables of wavelengths absorbed and emitted by atoms are available. Appendix 

1 lists the absorption wavelengths used to measure elements by AAS, discussed in Chapter 6. 

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