Short-wavelength stimulated emission limit in organic dye solutions

An analysis is made of the properties of the absorption spectra of complex organic molecules in the lowest electronic excited singlet and triplet states (induced absorption spectra). Stimulated emisssion due to fluorescence transitions in molecules with stimulated emission cross sections of the order of or smaller than 10^–18cm² is highly unlikely because of the unavoidable overlap of the induced absorption and fluorescnece spectra. Attempts were made to obtain ultraviolet stimulated emission in the 290–340 nm range in organic dye solutions. The absence of stimulated emission agreed with this conclusion and with the results of quantum-chemical calculations of the energies of the lowest excited singlet states and oscillator forces of the fluorescence transitions in various molecules.