Modern Polymer Spect..

Wavenumber, vI
Figure 1-10. A schematic contour diagram ofa synchronous
2D IR correlation spectrum 131. Shaded areas represent
negative correlation intensity.
I
n
Wavenumber, v,
Figure 1-11. A schematic contour diagram of an asynchronous
2D IR correlation spectrum [3]. Shaded areas represent
negative correlation intensity.
dynamic IR signals observed at two independently chosen wavenumbers. Plots of
correlation intensities as functions of two wavenumber axes are referred to as 2D
IR correlution spectra. Such spectra reveal important and useful information not
readily accessible from conventional one-dimensional spectra.
There are many different ways to plot a 2D IR correlation spectrum. A pseudothree-dimensional
representation (so-called fishnet plot) as shown in Figure 1-1 is
well suited for providing the overall features of a 2D IR spectrum. Usually, however,
2D IR spectra are more conveniently displayed as contour maps to indicate
clearly the location and intensity of peaks on a given spectral plane. In the following
section, basic properties of and information extracted from 2D IR spectra are
reviewed by using schematic contour maps (Figures 1-10 and 1-1 1).
1.3 Basic Properties of 2D IR Correlation Spectra
1.3.1 Synchronous 2D IR Spectrum
The correlation intensity at the diagonal position of a synchronous 2D spectrum
(Figure 1-10) corresponds to the autocorrelation function of perturbation-induced