Influence of the laser intensity on spectra

The previous few examples show that, under coherent illumination, one can no longer consider observed spectral intensities as purely characteristic of the atom, since the properties of the Autler-Townes doublet depend on the laser intensity, and the profile of a laser-excited autoionising line will in general possess a shape unrelated to that of an atom excited by a weak source. 

The implication is that laser spectroscopy brings out new phenomena which would not otherwise have been apparent, but also distorts the information so that it is not always simple to recover atomic parameters from observations of the spectra. This increased complexity becomes more and more apparent as the intensity of laser light is increased. 

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