Calculation And Measurement Of The Vibration Of Nitratelon

The nitrate is one of the important marine nutrients, it also plays a key role in atmospheric chemistry and nuclear waster treatment. The status of the nitrate ion in an aqueous solution is the fundamental to understand the mechanism of its actions.First of all, we use the Fourier Transform Infrared Spectrometry (FTIR) to measure the infrared absorption spectrum of the sodium nitrate solution with different concentrations and with other cations and anions. The infrared absorption spectrum shows that the antisymmetric stretching vibrationν₃(1350¹400cm^-1)has a strong infrared activity and splits into two vibrations. The cations and anions have a little influence on the vibration of nitrate.Next, we calculate the optimal structures of nitrate ion hydrated with 1-3 water molecules (NO₃^-·nH₂O,n=1³) using B3LYP of Density Function Theory(DFT). The calculation results show that there are several stable structures of the hydrate. Among these structures the antisymmetric stretching vibration of the NO₃^-·1H₂O is in good agreement with the infrared absorption spectrum of the nitrate solution. These results indicate that the interaction between nitrate anion and water molecules is essentially equivalent to the structure NO3-·1H2O. Furthermore, we also calculate the vibration frequency of the complex of hydrate nitrate with hydrate cation.