New experimental methods and theory of Raman optical activity

摘要

Abstract: Recent advances have led to dramatic improvements in the measurement of Raman optical activity (ROA). These include the use of new scattering geometries and improvements in polarization modulation methodology and multichannel-detector technology. Several new ROA experimental configurations are selected to illustrate the capabilities of a new ROA instrument constructed recently at Syracuse University. Both general and simplified theoretical expressions are used to identify fundamental aspects of various ROA experiments and to determine preferred configurations for the measurement of ROA. The authors find for their instrument that the optimum configuration is in-phase dual circular polarization (DCP$- I$/) ROA in backscattering geometry, as illustrated using ($PLU@)-fenchone. DCP$-I$/- ROA backscattering spectra are presented for aqueous solutions of L-alanine, glycyl-L-alanine and D-mannose. The large couplet arising from the bands between 800 and 900 cm$+$MIN@1$/ in the ROA spectrum of alanine is interpreted in terms of coupled methyl rocking and the methyl carbon-carbon stretching internal coordinates. The feasibility of applying ROA to the study of biological molecules is demonstrated by the high quality of the ROA spectra obtained for these molecules.!