Third harmonic generation spectra of degenerate ground state poly(dipropargyl) amines

We report third harmonic generation (THG) studies on solution-cast thin films of two poly(dipropargyl) amines, poly(N-hexyl dipropargylamine) (PDPHA) and a salt derivative, poly(dipropargyl-N-hexyl-N-methylammonium triflate) (PDPHMAT), covering pump energies from 0.6 to 1.4 eV. The THG data show the simultaneous two- and three-photon resonance expected for degenerate ground state conjugated polymers at 0.68 eV for PDPHA and 0.73 eV for PDPHMAT. The peak values of the third-order susceptibility are 1.0 × 10−10 esu for PDPHA and 2.9 × 10−11 esu for PDPHMAT; off-resonance values are nearly an order of magnitude smaller.