Eur. Phys. J. B 47, 341-361 (2005)
https://doi.org/10.1140/epjb/e2005-00341-x

Transient grating experiments on supercooled molecular liquids II: microscopic derivation of the phenomenological equations

¹ Hahn-Meitner Institut, 14109 Berlin, Germany
² Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universität München, 80333 München, Germany
³ IMPMC, UPMC, 4 Place Jussieu, 75005 Paris, France

Corresponding author: ^a cor@ccr.jussieu.fr

Received: 14 April 2005
Published online: 28 October 2005

Abstract

The constitutive equations including the energy conservation aspect, for the long-wavelength dynamics of a liquid comprised of identical, axially symmetric, rigid molecules are microscopically derived. These equations are extended to the case where the dynamics is generated by the interactions of two coherent lasers (the pumps) with the liquid. This interaction corresponds to a weak energy absorption and also to the coupling of the pumps with fluctuations in the mass density, the molecular orientation density and the temperature of the liquid. The microscopic equations generalise those phenomenologically derived in Pick et al. [1] where the role of the temperature fluctuations was ignored. Constraints on the relaxation functions related to the temperature fluctuations and to their coupling with density are derived.