THE HYDRATION STRUCTURE OF NO3- IN CONCENTRATED AQUEOUS SODIUM-NITRATE SOLUTIONS

Time-of-flight neutron diffraction measurements have been carried out on 10 mol% NaNO3 solution in D2O. The isotopic substitution technique was applied to nitrogen atoms in the solution in order to determine bo th hydration structure around the nitrate ion, NO3-, and intramolecula r geometry of NO3- in the aqueous solution. It has become apparent tha t there exist 5.0+/-0.5 water molecules coordinated to NO3- with the i ntermolecular distance r(N...D) = 2.80 angstrom. The intramolecular bo nd distance and the root mean square amplitude in NO3- have been deter mined to be r(NO) = 1.253+/-0.006 angstrom and l(NO) = 0.058+/-0.008 a ngstrom, respectively.