Structural Decomposition of UV--Visible Spectral Variation: Azobenzene in Ethanol Solution

Abstract

We present a structural interpretation of statistical variability in simulated liquid-phase UV--visible absorption spectra. We analyze the significant variation of the spectral response, caused by structural variation within the ensemble, using a response-targeted method known as emulator-based component analysis. In the high-dimensional input space, the method identifies a subspace of a few dimensions that accounts for most spectral variance. The resulting decomposition reveals the spectrally decisive structural features and filters out the irrelevant ones. For our test case, the ethanolic {\it trans}-azobenzene, the analysis implies an overrepresentation of certain structural characteristics following a photoexcitation at a given wavelength, potentially significant for the subsequent nuclear dynamics, photophysics, and photochemistry.