to accurately model excited states of nitrate anion under solvation. All the TDDFT calculations were performed using a triple-ζ valence polarized Karlsruhe (def2-TZVP) basis set along with the resolution of identity approximation for the Coulomb and exchange integrals. The UV-visible spectra are obtained from the Gaussian envelopes with an empirical broadening width σ of 0.027 eV. UV-Visible absorption spectra calculations were performed using ORCA 5.0.1 package. To account for the effect of ion pairing at the surface of ice, we have computed separately the absorption spectra of the molecular complexes made of NO - 3 paired with either NH + 4 or NH 3 , treating ammonium/ammonia explicitly together with the water solvation shell. These systems are embedded in a hybrid solvation model, where the first two solvation shells of NO - 3 , which correspond to 12 water molecules, are treated explicitly, and the long-range screening is accounted for by the CPCM polarizable implicit solvent, with a static dielectric constant of 80.3 and refractive index 1.33. Svoboda, et. al, calculated the electronic absorption spectra of isolated and solvated nitrate anion in the UV region and found that adding beyond 10 explicit water molecules does not modify the predicted spectra.