Hi! I'm a little confused about simple spectroscopy. In typical absorption experiments, we scan the laser frequency w and get a anti-peak/dip in the transmitted intensity I(w) around a resonance frequency. The size of the dip, i.e. the population of the excited level, usually depends linearly on the laser intensity. How can this be understood from first principles?(adsbygoogle = window.adsbygoogle || []).push({});

I know about Rabi oscillations in optically driven two level systems, but these are of course quite different. I have also studied more advanced descriptions -density matrices, master equations like the optical Bloch equations, etc.- but I'm still kind of stuck with this simple question.

Thanks in advance!

photon stew

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# Explaining linear spectroscopy from first principles

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