Molecular hydrodynamic theory of nonresonant Raman spectra in liquids: Fifth-order spectra

Building upon the framework of the preceding paper, a molecular hydrodynamic theory of the fifth-order (two-dimensional) nonresonant Raman spectrum in a simple liquid is presented. A multi-time mode-coupling-like theory is developed and compared with recent computer simulations for liquid Xe. The theory is able to provide a microscopic rationale for the absence of an echo in this system. Experimental predictions for the temperature and density dependence of the signal are presented. Comparison is made with the instantaneous-normal-mode theory. The limitations of the present approach are discussed.(C) 2002 American Institute of Physics.