Two-dimensional infrared correlation spectroscopy: Global phase angles for specific analytical systems

In this paper we discuss further properties of 2D correlation spectroscopy using the global phase angle intensity normalization method. The 2D global phase angle analysis method has been shown to discriminate against arbitrary signal amplitude changes not related to real correlation intensities. We have confirmed that the positive or negative sign of a global phase angle 2D correlation peak is a direct expression of the sequential order of signal intensity changes. We have derived analytical solutions for 2D correlation algorithms using the global phase angle based on sinusoidal, exponential decay, and Lorentzian model functions. These derivations show that the experimental determination of the global phase angle can provide a quantitative measurement of sequential order when using these specific analytical models.