To understand the nature of the intramolecular vibrational modes most responsible for the decoherence, we have modeled the resonance Raman spectra using timedependent density functional theory (TD-DFT) (computational details are included in the Materials and Methods). To keep the computations tractable, we focus on the RR spectra of thymine as the spectral features of the nucleoside and nucleotide are nearly identical and thus vibrational assignments in thymine are expected to also apply in the other two cases. Quantitative agreement between theory and experiment is obtained by including four explicit water molecules in the first solvation shell that are an active part of the vibrational motion of the molecule in its microsolvated environment and that are significantly coupled to the electronic transition.