Diagnostic properties of two-photon-pumped stimulated emission in atmospheric species
Two-photon excitation provides access to atoms and molecules with absorption resonances in the vacuum ultraviolet (VUV), i.e., to the species otherwise inaccessible for probing under atmospheric conditions, since the atmosphere strongly absorbs VUV radiation. In addition, for high enough laser intensities, two-photon pumping may create population inversion between the pumped energy state and a low