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Effect of the Dynamical Disorder on the Second-Order Nonlinear Optical Responses of Helicity-Encoded Polymer Strands

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journal contribution
posted on 18.06.2009, 00:00 by Raphaël Méreau, Frédéric Castet, Edith Botek, Benoît Champagne
By combining classical samplings with quantum chemistry semiempirical time-dependent Hartree−Fock calculations, the high impact of dynamic fluctuations on the NLO properties of helical strands has been evidenced. In particular, these fluctuations are responsible for relative variations of ∼20% in the hyper-Rayleigh responses in both pyridine−pyrimidine (py−pym) and hydrazone−pyrimidine (hy−pym) strands. Then, dynamical disorder has an even more important impact on the electric-field-induced second harmonic generation responses, whose variations can reach 2 (py−pym) or 5 (hy−pym) times their mean value. This work also highlights the relationships between the unit cell nature and helical conformation of foldamers and their second-order NLO responses. In particular, the octupolar symmetry of the hyper-Rayleigh depolarization ratios is related to the helix periodicity of three unit cells per turn in both compounds.

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