The temperature dependence of the Kerr constant of polar liquids

Abstract

The temperature dependences of the Kerr constants of ten polar liquids in the range 275-343 K are reported. They are H₂O, D₂O, MeOH, Bu^tOH, CHCl₃, MeCN, PhCl, Me₂SO, Me₂CO and MeNO₂. The Kerr constants of all the liquids were found to have a T-1 and T-2 dependence, except for Bu^tOH which had an exp(-U/RT) dependence, where U is 28.0 kJ/mol. The Kerr effect, a sensitive probe of liquid structure, is related to the polarization <P₁(cos θ)>_E and alignment<P₂(cos θ)>_E where P_i(cosθ)(i = 1, 2) are the first and second Legendre polynomials respectively, and θ is the angle between the dipole axis of the reference molecule and the applied field. For the liquids consisting of the axially symmetric molecules CHCl₃ and MeCN, we combine Kerr effect, dielectric and light scattering data to analyse the temperature dependence of <P₂(cos θ)>_E, to obtain information about two- and three-particle correlation functions. We also present a qualitative discussion of the other liquids.