Dipole moment of aniline in the excited S1 state from thermochromic effect on electronic spectra

Using the thermochromic shift method of absorption and fluorescence spectra of aniline in ethyl acetate for temperature ranging from 213 to 393 K, the change of the dipole moment Δμ = μe − μg = 0.84 D between the ground and first excited singlet state was determined based on the Bilot and Kawski theory. This is in agreement with the result obtained by Lombardi from optical Stark effect in the rotational fine structure. For the known dipole moment in the ground state μg = 1.53 D and for α/a3 = 0.483 (α is the polarizability and a is the Onsager interaction radius of the solute) the average value of μe = 2.37 D and a = 2.7 Å were determined. The values obtained for aniline are compared with the experimental values determined by other authors.