In 1931, Mayer described the two-photon absorption process in her dissertation, a foundational concept in nonlinear optics.
In her doctoral dissertation completed in 1931, Maria Goeppert Mayer provided the first theoretical description of the two-photon absorption process, introducing what is now recognized as a foundational concept in nonlinear optics. This marked the first time two-photon absorption was described in a dissertation, furthering quantum mechanics by elucidating how atoms absorb photons.