On the discrepancy between theoretical calculation and experimental observation of second hyperpolarizability of furan homologues

Frequency dispersion of second hyperpolarizability of furan homologues is calculated by the time-dependent Hartree–Fock (TDHF) method. Using the calculated results, the most reliable theoretical values for the second hyperpolarizability are estimated including both effects of electron correlation and frequency dispersion with the comparison of several approximation methods. The estimated values are compared with the observed values measured by the optical Kerr effect (OKE) method. It is found that by inclusion of the effect of frequency dispersion the calculated results approach more closely to the observed values especially for the molecules with heavier hetero atoms like thiophene, selenophene or tellurophene.