Temperature-dependent infrared spectra of the asymmetric stretch region of aqueous nitrate ion solutions indicate a subtle a change in peakshape which implies that the relative energy for different solvation geometries is on the order of thermal energy at room temperature. Further, ionic strength modulates the difference in such a way that these differences become negligible at high electrolyte concentrations. Mixed quantum-classical simulations and electrostatic-potential-to-vibrational-frequency correlations reproduce some of these features, but slightly overestimate the peak splitting between the symmetry-broken asymmetric stretches. The effect of electric field on optimized nitrate ion molecular geometry is extremely small, but the effect of electronic redistribution is sufficient to change the vibrational frequencies by 8 to 50 cm-1, depending on the vibrational mode.

Local electric fields and symmetry breaking in nitrate ion

248th National Meeting (2014)

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