Global Phase Angle Description of Generalized Two-Dimensional Correlation Spectroscopy: 1. Theory and its Simulation for Practical Use

Abstract

The concept of a global phase map derived from generalized twodimensional synchronous and asynchronous correlation spectra is introduced to extract the purely correlational information by intentionally canceling amplitude information. For the practical usage of a global 2D phase map, a ltering method based on the standard deviation spectrum obtained from the time series intensity pro les is proposed to remove the effect of small amplitude noise. A simulation created with the use of three synthesized bands with exponential decay has clearly detected the only difference in the characteristic rate constant of the decay process in the global 2D phase map, although the three bands have different initial values of the peak intensity amplitudes.

Advances in two-dimensional correlation spectroscopy

“…The use of slice spectra [39] is often seen in the detailed 2D analysis, as it provides the fine features of intensity variations in a more familiar 1D form. Display filter for 2D map, based on the standard deviation as a threshold to suppress noise contamination, was proposed by Morita et al [40]. The method is especially useful for normalized 2D spectra, such as global phase and correlation coefficient maps, since they tend to disproportionately accentuate the effect of noise in the lowsignal region.…”

Two-dimensional correlation spectroscopy — Biannual survey 2007–2009

“…The arctangent of coherence is the 2D global phase angle, which provides a semi-quantitative measure of the sequential ordering of the spectral intensity changes [86,87]. Shinzawa et al [88] proposed a new use of global phase angle as a convergence criterion for the alternating least squares (ALS) algorithm used in multivariate curve resolution (MCR) analysis.…”

The application of two‐dimensional correlation spectroscopy to surface and interfacial analysis

“…To deal with the problem of artificially enhanced noise often associated with amplitude normalization in 2D COS, Morita et al 233 proposed the idea of signal filtering that allows one to blind the unwanted noise contribution. This method has been termed the global 2D phase map.…”

“…The parameter υ is selected using the standard deviation spectrum of the signal measured at wavenumber position . 233 The standard deviation spectrum SD( ) is given by the square root of ( , ). 233 Although the selection of υ is arbitrary, it is recommended to set the value of υ as ten times that of a standard deviation value in the baseline region.…”

“…233 The standard deviation spectrum SD( ) is given by the square root of ( , ). 233 Although the selection of υ is arbitrary, it is recommended to set the value of υ as ten times that of a standard deviation value in the baseline region. This parameter setting ensures that potential artifacts from the contribution of weak signal regions are rejected.…”