Depolarization ratio hyperpolarizability

B1.3.2.5 THE MICROSCOPIC HYPERPOLARIZABILITY TENSOR, ORIENTATIONAL AVERAGING, THE KRAMERS-HEISENBERG EXPRESSION AND DEPOLARIZATION RATIOS... 

By combining classical samplings with quantum chemistry semiempirical TDHF calculations the impact of dynamic fluctuations on the first hyperpolarizability 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. 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. These results demonstrate that geometrical fluctuations have to be taken into account for a reliable description of the second-order NLO properties in flexible structures such as helical strands. This work has also highlighted the relationships between the nature of the unit cell and the helical conformation of foldamers and their second-order NLO responses. In particular, the value of the hyper-Rayleigh depolarization ratio, which is characteristics of octupolar symmetry, is related to the helix periodicity, of three unit cells per turn in both compounds. 

Table 8.2 Basis set effects on the TDHF (2= 1064nm) first hyperpolarizability (fSn and hrsI depolarization ratio, and dipole moment of the E and K tautomeric forms of compound 4.

Table 8.3 Static EFISHG and HRS first hyperpolarizabilities (/ // and in a.u.) and depolarization ratios (DR) of the E and K tautomeric forms of substituted Schiff bases obtained at the MP2/cc-pVDZ level using MP2/6-31G optimized geometries.

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