Two-Dimensional Correlation Spectroscopy Study of Temperature-Dependent Spectral Variations of N-Methylacetamide in the Pure Liquid State. 2. Two-Dimensional Raman and Infrared−Raman Heterospectral Analysis

Abstract

This paper demonstrates the potential of two-dimensional infrared−Raman (2D IR-Raman) heterospectral correlation spectroscopy in analyses of IR and Raman spectra of complex systems and of correlations between IR and Raman bands. Temperature-dependent spectral variations of N-methylacetamide (NMA) in the pure liquid state have been investigated as the first example of 2D IR-Raman correlation spectroscopy study. IR and Raman spectra of NMA in the pure liquid state have been measured over a temperature range of 30−65 °C. Generalized 2D Raman correlation spectroscopy has been also performed to assist the 2D IR-Raman correlation analysis. The 2D Raman correlation spectroscopic analysis reveals that the amide I Raman band of NMA consists of at least three distinct bands at 1665, 1650, and 1635 cm-1, and the 2D IR-Raman study shows that they are correlated with the amide I IR bands at the same frequencies, respectively. In the preceding paper, these IR bands at 1635, 1650, and 1665 cm-1 have been ascribed to lar...