Question

c) For quantitative measurements of concetration in atomic absorption spectroscopy ie with hallow cathode lamp. Why is it critical that the line width of radiation source be much narrower than the absorption line of the sample?

Answer 1

One of the greatest advantage of Atomic Absorption Spectroscopy, namely its specificity, is based on the use of specific radiation source that emits the spectrum of the analyte element in the form of very narrow spectral lines. The ability of AAS to differentiate between different elements is solely dependent on the half intensity widths of the emission line.

When hollow cathode lamp is used as a source of radiation the monochromator in AAS has the important task of separating the resonance line of analyte element from other emission lines of the source. If slit widths are larger in AAS, lower sensitivity and increasing non-resolving multiplets result (several resonance lines passing through the exit slit).

With a sufficiently small sit-width, resulting in narrow line width, every resonance line gives a linear analytical curve.