Experimental and theoretical investigations of reference molecules for nonlinear optics: The example of acetonitrile

We present a joint experimental and quantum chemical investigation on the first hyperpolarizability of the acetonitrile molecule, which is used as an external reference in Hyper-Rayleigh scattering (HRS) experiments. The measured HRS response is compared with calculations using the Finite Field (FF) procedure in combination with the Hartree-Fock and MP2 methods. Solvent effects are accounted for by using the Polarizable Continuum Model, while frequency dispersion effects are included by using a multiplicative correction scheme.