Hyperpolarizabilities of the m-substituent phenyl amine based chromophores determined from the hyper-Rayleigh scattering and two photon absorption induced fluorescence

The technique of hyper-Rayleigh scattering is used to determine and compare the first hyperpolarizabilities (beta) of five structurally similar m-substituent phenyl-amine based chromophores using both internal and external standards. Contribution from the two photon absorption induced fluorescence to the observed signal is carefully removed. The chromophores with the m-substituted phenyl ring, that stabilizes the maximal charge-transfer state through resonance effect, are found to have larger static beta values and redshifted electronic absorption peaks (lambda(max)) compared with the para-nitroaniline (pNA) chromophore. The electron-withdrawing m-substituent of the chromophore is found to have the effect of reducing both the beta and lambda(max) values. Its effect on beta is less pronounced when the pi-electron reservoir is large, The enhancement of beta value and the redshift lambda(max) are observed to be consistent with the extent of the pi electron delocalization. (C) 1996 American Institute of Physics.