The use of neutrons in the analysis of the non-linear optical phenomenon

An extensive program of accurate charge-density (CD) studies has been undertaken on four series of organic non-linear-optical (NLO) materials. The aim was to obtain a detailed understanding of the nature of the charge-transfer (CT) processes occurring within each molecule and determine the molecular (hyper)polarizability coefficients for each compound. CD studies also provide limited information about the nature of the intermolecular forces. More information has been obtained using coherent inelastic neutron scattering (CINS) to measure the three-dimensional phonon dispersion of one novel organometallic NLO compound, zinc (tris) thiourea sulphate. An overview of our results to date are presented.