The first observation to our knowledge of a second-order nonlinear optical effect in a nonpolar molecular ion is reported. Hyper-Rayleigh scattering was observed from aqueous and organic solutions of the tricyanomethanide ion [C(CN)3]−. Because of the absence of a dipole moment and the presence of a charge in this planar, nonpolar, but highly polarizable molecular anion with D3h symmetry, no electric-field-induced second-harmonic-generation experiments are possible. The experimental values for the first hyperpolarizability βxxx [(7 ± 1.5) × 10−30 esu, independent of the solvent] are in good agreement with the results from quantum-chemical calculations.
© 1993 Optical Society of America
Original Manuscript: September 17, 1992
Published: April 1, 1993
T. Verbiest, F. Meyers, J. L. Brédas, K. Clays, and A. Persoons, "Determination of the hyperpolarizability of an octopolar molecular ion by hyper-Rayleigh scattering," Opt. Lett. 18, 525-527 (1993)