Anisotropic second-order nonlinearities of organic monolayers

Monolayers prepared from hemicyanine chromophores of high second-order nonlinearity ({β}=1.3×{}10^-26 esu at resonance) have been used to study anisotropies of the concomitant χ⁽²⁾-susceptibility tensor. All components of this third-rank tensor have been determined by Fourier analysis of the anisotropic coverage density Nₛ({φ}) with respect to the angle of rotation about surface normal. Depending on the preparation both Cₛ and C₂ᵥ symmetry could be identified.