Cooperative second harmonic laser light scattering in liquid cyclohexane, benzene and carbon disulphide

Using a Q ‐switched Nd: glass laser with a high transmission optical system, first measurements of cooperative second harmonic light scattering (SHLS) in liquid cyclohexane, benzene and carbon disulphide were performed. Molecular‐statistical theory is extended to show that cooperative SHLS by liquids consisting of centro‐symmetric molecules is due to a lowering of their symmetry by the time and space fluctuating electric field of the quadrupoles and hexadecapoles of near neighbouring molecules. Also, the rôle of angular molecular correlations as well as of anisotropy in third‐order nonlinear polarisability of the scattering molecules is discussed.