Reference molecules for nonlinear optics: A joint experimental and theoretical investigation

Abstract

Hyper-Rayleigh scattering (HRS) experiments and quantum chemical calculations are combined to investigate the second-order nonlinear optical responses of a series of reference molecules, namely, carbon tetrachloride, chloroform, trichloroacetonitrile, acetonitrile, and dichloromethane. The multipolar decomposition of the first hyperpolarizability tensor through the use of the spherical harmonics formalism is employed to highlight the impact of the symmetry of the molecular scatterers on their nonlinear optical responses. It is demonstrated that HRS is a technique of choice to probe the molecular symmetry of the compounds. Coupled-cluster calculations performed at the coupled-cluster level with singles, doubles, and perturbative triples in combination with highly extended basis sets and including environment effects by using the polarizable continuum model qualitatively reproduce the molecular first hyperpolarizabilities and depolarization ratios of the molecular scatterers.

Interpreting the First-Order Electronic Hyperpolarizability for a Series of Octupolar Push–Pull Triarylamine Molecules Containing Trifluoromethyl

“…41 The nonlinear anisotropy parameter ρ = |β J=3 | 2 /|β J=1 | 2 compares the relative contributions of the octupolar [Φ(β J=3 ) = ρ/(1 + ρ)] and dipolar [Φ(β J=1 ) = 1 − Φ(β J=3 )] components to the first-order hyperpolarizability tensor β. Such parameter provides a quantitative classification of the molecular system in terms of its more or less pronounced octupolar/dipolar character.…”

Synthesis, spectroscopic and DFT Characterization of 4β-(4-tert-Butylphenoxy)phthalocyanine positional isomers for non-linear optical absorption

“…The values of both dipolar (b J=1 ) and octupolar (b J=3 ) are known to be significantly influenced by the number of electrons in the system. 23 Due to symmetry constraints there is no permanent dipole moment for octupolar molecules, 25 hence octupolar molecules present an isotropic b tensor.…”

“…The nature of the symmetric Rank-3 b tensor is further clarified by decomposing b HRS 2 as the sum of the dipolar (b J=1 ) and octupolar (b J=3 ) tensorial components, 25 which are expressed as Equations (6) and (7):…”

“…The theoretical normalized HRS intensity (I y n w 2 ) is determined by using Bersohn's expression, 25 Equation (8), which assumes a general elliptically polarized incident light propagating along the X direction. Equation (8) further assumes that the intensity of the harmonic light is scattered at 90°along the Y direction and the vertically (V) polarized light along the Z axis.…”

“…DFT calculation of hyper-Rayleigh Scattering (HRS) response coefficient (b HRS ) was carried out in order to calculate the first static hyperpolarizability (second-order hyperpolarizability), following literature methods [23][24][25][26] The advantage of this method is that octupolar and dipolar second-order NLO contributions are theoretically separated. The values of both dipolar (b J=1 ) and octupolar (b J=3 ) are known to be significantly influenced by the number of electrons in the system.…”