Nonresonant femtosecond second hyperpolarizabilities of intramolecular charge-transfer molecules with great excited- and ground-state dipole-moment differences

The femtosecond second hyperpolarizability due to the nonresonant electronic polarization for two intramolecular charge-transfer molecules, 6-propionyl-2-dimethylamino naphthalene and 2-anilinonaphthalene-6-sulfonic acid which possess the great permanent dipole-moment difference between the excited state and the ground state, is obtained from the measurement of the ultrafast change in refractive index using a time-resolved interferometer. It is found that the second hyperpolarizability increases parabolically from 5×10−34 to 4.3×10−32 esu with increasing the dipole-moment difference from 7.7 to 40 D, and this quantitative relationship is well explained by a quantum-mechanical equation describing the electronic second hyperpolarizability of one molecule with the permanent dipole-moment difference.