Experimental vibrational contributions to molecular hyperpolarisabilities:methods and measurements

The aim of this paper is to give a simple but a complete guide to the exper imental determination of vibrational molecular first and second hyperpolari sabilities from measurements of band frequencies and intensities in vibrati onal (IR and Raman) spectra. The approximations involved in the method are discussed and a comparison with the theoretical results is presented. A bri ef summary of the many applications of the "vibrational method" and a criti cal discussion of the problems involved are also reported. (C) 2000 Elsevie r Science B.V. All rights reserved.