A critical examination of two-photon absorption cross-sections of some reference dyes

The electronic structure and one- and two-photon absorption spectra of four most commonly used Flurophores, namely Bis-MSB, Coumarin 307, Fluorescein and Rhodamine B has been theoretically calculated and compared with experimentally reported spectra. The possible reasons for discrepancies in two photon absorption cross-sections reported in the literature till date is discussed. Since, our calculations are independent of laser source and different calibration methods used by different experimental groups, it should provide, at least in principle, a good picture about the electronic structure. The effect of solvent on the electronic one photon as well as two photon absorption spectra is also obtained. Finally, we also discuss about the necessary precautions that one needs to take when they compare their results with the one already reported in the literature.