The self-aggregation of Rhodamine - 6G [1 x 10-6 to 4 x 10-4] in water and in aqueous solution of Bu4NBr (0.1 - 0.3 M) has been investigated by recording electronic spectra in the wavelength range 460 to 600 nm. Analysis of the spectral data yielded the dimer dissociation constant, individual characteristic monomer and dimer spectra. By applying the excitation model for the first time, the interaction energy between the Rhodamine - 6G molecules in dimer species has been evaluated. Further information about the dimer geometry and twist angle between the dipoles of the Rh-6G molecules has been obtained.
