Bathochromic shift in the UV-visible absorption spectra of phenols at ice surfaces: insights from first-principles calculations

Some organic pollutants in snowpack undergo faster photodegradation than in solution. One possible explanation for such effect is that their UV-visible absorption spectra are shifted toward lower energy when the molecules are adsorbed at the air-ice interface. However, such bathochromic shift is difficult to measure experimentally. Here we employ a multiscale/multimodel approach that combines classical and first-principles molecular dynamics, quantum chemical methods and statistical learning to compute the light absorption spectra of two phenolic molecules in different solvation environments at the relevant thermodynamic conditions. Our calculations provide an accurate estimate of the bathochromic shift of the lowest-energy UV-visible absorption band when these molecules are adsorbed at the air-ice interface, and they shed light into its molecular origin.