Relative intensity correction of Raman optical activity spectra facilitates extending the spectral region
Abstract
Using home-built Raman optical activity (ROA) spectrometer and a relative intensity correction for different instrument responses, we report ROA spectra beyond the traditionally utilized spectral region of 200-2500 cm(-1). With three different interchangeable gratings covering partially overlapping spectral regions, we can study ROA in the whole region of fundamental molecular vibrations (150-4000 cm(-1)).
Complete panoramic spectra are assembled from subparts collected with different gratings after a relative intensity correction based on the National Institute of Science and Technology standards known from the analogous application in Raman and fluorescence spectroscopy. Using this setup, we report the still little known ROA from C-H and C-D stretching region of the testing substances alpha-pinene and a tricyclic spirodilactam.
The intensity-corrected experimental data were compared with calculated ROA and Raman spectra of these substances both with and without anharmonic corrections. A comparison revealed that above 1200 cm(-1), the anharmonic correction provides a clear improvement of the agreement.
While the calculation of Raman spectra achieves already good accuracy, the analogous ROA calculations still need further development.