2D correlation analysis: sequential order judging

Area of Science:

• Spectroscopy
• Chemical Physics
• Data Analysis

Background:

• Two-dimensional (2D) correlation analysis is widely used to determine the sequence of physical or chemical events.
• Existing methods for determining sequential order can lead to ambiguous or incorrect conclusions.
• The physical significance of sequential order in generalized 2D correlation analysis is not always well-defined.

Purpose of the Study:

• To critically evaluate the "sequential order" rules in 2D correlation analysis.
• To differentiate between integrated sequential order and local/chronological sequential order.
• To establish a more reliable method for determining event sequences, especially for nonperiodic changes.

Main Methods:

• Analysis of generalized 2D correlation analysis principles.
• Comparison of integrated sequential order (periodic changes) with local/chronological sequential order (nonperiodic changes).
• Investigation of phase sequence/difference in relation to integrated sequential order.

Main Results:

• The "sequential order" rules in 2D correlation analysis can yield ambiguous results due to ill-defined physical significance.
• Integrated sequential order reflects phase sequence and is meaningful for periodic changes under consistent conditions.
• For nonperiodic changes, integrated sequential order is unreliable; local/chronological sequential order, verified by original spectral intensity changes, is necessary.

Conclusions:

• The interpretation of "sequential order" in 2D correlation analysis requires careful consideration of the nature of the changes (periodic vs. nonperiodic).
• For nonperiodic events, relying solely on integrated sequential order can lead to errors; chronological verification is essential.
• This work emphasizes the importance of distinguishing and correctly applying different types of sequential order determination in spectroscopic analysis.