Abstract
In this paper I propose a Di-Dj plot method that expresses pairs of ith and jth derivatives in a two-dimensional representation as a rational method to describe spectral waveforms. The basic concepts of the method are explained, and some examples of its applications are given to demonstrate the usefulness of the method in spectral analysis. First, I discuss the effects of plotting the correlations of derivatives of different powers-second vs. first and third vs. fourth-to separate adjacent bands, as well as the effect of adding a nonflat background to the spectrum. Next, a number of derivative correlation plots for Gaussian and Lorentzian shaped bands are described. Third, I show how the method can be used to determine the presence of an underlying band and how to extract the two bands from the original band. As examples of its applications, a waveform analysis of infrared spectra, the determination of the optimum cell pathlength for a water sample, and an analysis of temperature-dependent changes in a near-infrared (NIR) spectrum for water are discussed.
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