The SGCI–SISSI Framework: A Spectral–Geometric Coherence Index for Vibrational Analysis

SGCI–SISSI (Spectral Generalized Coherence Index – Spectral Information Similarity System Interface) introduces a new quantitative framework for analyzing spectral similarity and vibrational coherence between molecular systems. Unlike traditional approaches (e.g., cross-correlation, cosine similarity, or PCA), SISSI applies a dynamic, physically grounded weighting of spectral differences, allowing for the identification of coherent or dissonant vibrational patterns while preserving physical interpretability. The method enables transparent comparison of molecular and isotopic spectra, revealing how structural or isotopic substitutions influence vibrational information flow. SISSI can be applied to FT-IR, Raman, NMR, and even theoretical or simulated data, providing a unifying measure of coherence that bridges physics, chemistry, and information theory. This work presents the algorithmic foundation, validation on experimental datasets, and implications for understanding vibrational information transfer, with potential applications in spectroscopy, materials science, and quantum information. Author: Giovanni Amato (© 2025, CC BY 4.0 License)