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, ButOH, 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 ButOH 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 Pi(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.