Ultraviolet discharge in electrodeless lamp

Very many of the advantages of AAS can be directly or indirectly traced to the narrow half-intensity width of the resonance lines, i.e., the absorption of an element takes place within a very limited spectral range of about O.OOl-O.OOS nm. This advantage becomes very noticeable if the radiation sources used for excitation emit the spectrum of the analyte element in spectral lines that are narrower than the absorption lines. Hollow cathode lamps (HCLs) and electrodeless discharge lamps (EDLs) are particularly suitable as radiation sources. The latter typically provide a higher radiation intensity which results in a better signal-to-noise (S/N) ratio, particularly in the far-ultraviolet (UV) range of the spectrum. Radiation sources that emit a continuous spectrum are... 

Sources that emit a few discrete lines find wide use in atomic absorption spectroscopy, atomic and molecular fluorescence spectroscopy, and Raman spectroscopy (refractometry and polarimetry also use line sources). The familiar mercury and sodium vapor lamps provide a relatively few sharp lines in the ultraviolet and visible regions and are used in several spectroscopic instruments, Hollow-cathode lamps and electrodeless discharge lamps are the most important line sources for atomic absorption and fluorescence methods. Discussion of such sources is deferred to Section 9B-1. 

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