βν-Correlation Analysis: A Modified Two-Dimensional Infrared Correlation Method for Determining Relative Rates of Intensity Change

A modified two-dimensional infrared (2D IR) correlation method called βν correlation analysis is introduced for quantitatively determining the relative rates of intensity change and the degree of coherence between intensity variations in a discrete set of dynamic spectra. In a βν correlation analysis, a mathematical cross correlation is performed between a set of n spectra undergoing some dynamic intensity variation, i.e. f (ν,n), against a simple mathematical function. In the present case this is a sine function. Correlation intensities are a function of the phase angle (β) of the sinusoidal function and the spectral frequency (ν). The maximum positive correlation intensity will be observed at one point in the asynchronous (β,ν) correlation plot for the range 360° > β ≥ 0°. This point is used to define a new parameter, the effective phase angle, βe, of f (ν,n), where βe is simply equal to β + 90°. In graphical terms, βe is the point of maximum positive correlation intensity in the asynchronous β vs. ν pl...