We present a joint experimental and theoretical study of the non-linear optical (NLO) spectroscopy of correlated π-electrons in a conjugated polymer. Spectra of two NLO coefficients, the third harmonic generation efficiency (THG) and two-photon absorption (TPA) cross-section, are reported using polydiacetylene-4BCMU. The THG spectrum is dominated by states near the optical gap (Eg), similar to the behavior seen in the linear absorption spectrum, but the TPA onsets below Eg and its spectrum is dominated by states well above it. These experimental spectra are accounted for by exact calculations based on correlated electrons model of a conjugated polymer. © 1991.
Townsend, P. D., Fann, W. S., Etemad, S., Baker, G. L., Soos, Z. G., & McWilliams, P. C. M. (1991). Non-linear optical spectroscopy of correlated π-electrons in a one-dimensional semiconductor. Chemical Physics Letters, 180(5), 485–489. https://doi.org/10.1016/0009-2614(91)85155-P