Absorption band maxima of pyridinium-N-phenoxide betaine-30 [C. Reichardt, Chem. Rev. 94 (1994) 2319] are investigated as a function of refractive index and static permittivity of solvents. Spectral shift components due to dispersive forces and solvent polarization were separated, revealing a large increase of polarizability from 70 angstrom(3) in the ground state to similar to 200 angstrom(3) in the excited state. Optical band maximum of the nonsolvated chromophore in vacuum is predicted by extrapolation to lie at 40.3 +/- 2 kcal/mol, close to the E-T(30) value in methyl acetate (38.9 kcal/ mol). The contributions of repulsive, dispersive, inductive, and reaction field effects are discussed. (C) 2008 Elsevier B.V. All rights reserved.