Meyer, Maria

That the simultaneous absorption of two (or more) photons [Eq. (7.3)] to generate an excited state is possible was predicted theoretically by Maria Goppert Meyer [13] in 1931 (the unit of cross section has been named in her honor, 1 GM = 8= 1 X 10 ° cm" s photon ), although the likelihood of such phenomenon is quite poor, and its occurrence was demonstrated much later, when high-intensity lasers became available. 

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