Atomic absorption spectroscopy yields extremely narrow signals. It is difficult to separate white light with sufficient precision using monochromators, and hollow cathode lamps are often used as light sources instead. Disadvantage: a different lamp is needed for each element we wish to measure.

Why aren't lasers used as light sources? Lasers are perfectly monochromatic, and tunable lasers could be set to match absorption bands of many elements.

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    $\begingroup$ It could be because the lasers with the widest wavelength range have bandwidths that are too broad and the the lasers with narrow bandwidths don't have the same ability to tune over very large ranges of wavelength. $\endgroup$ – matt_black Jun 22 '18 at 12:58
  • $\begingroup$ Mainly cost and ease of use. Lasers are expensive and hard to maintain with narrow bandwidths and have limited wavelength tuning. Cathode are, in comparison, dirt cheap. (In fact atomic lines are actually not that narrow and nowadays lasers can have line - widths orders of magnitude narrower than atomic lines. ) $\endgroup$ – porphyrin Jun 22 '18 at 19:37

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