Destructive Interference of Imaginary Resonant Contributions toχ(3)

The first observation of destructive interference of imaginary contributions to ${\chi }^{\mathrm{}\left(3\right)\mathrm{}}$ from different resonances is reported. Destructive and constructive interferences were obtained between Raman and two-photon absorption (TPA) contributions in organic liquids. Accurate TPA and two-photon dispersion spectra of C${\mathrm{S}}_2$ obtained by using these interferences in ${\chi }^{\mathrm{}\left(3\right)\mathrm{}}$ are reported. The TPA experiment described is superior to the classical TPA experiments in its accuracy and in the fact that it lacks the uncertainties originating from scattering processes which compete with true TPA.