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Raman study of the symmetric ν 1 vibrational mode of N 3 − and NO 3 − in aqueous solutions
Author(s) -
Dean K. J.,
Wilkinson G. R.
Publication year - 1985
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250160105
Subject(s) - chemistry , aqueous solution , dilution , excited state , ion , alkali metal , analytical chemistry (journal) , inorganic chemistry , atomic physics , physics , thermodynamics , organic chemistry , chromatography
The totally symmetric ν 1 vibrational modes of the anions N 3 − and NO 3 − have been studied in aqueous solution with very high precision. The effect of different alkali metal cations (Li + , Na + , K + , Rb + and Cs + ) has been systematically recorded as a function of the solution concentration. The experimental results show that the anion ν 1 mode frequencies are dependent on both the cation present and on the solution concentration. Extrapolation of the experimental data yielded precise values of the anion ν 1 frequencies in the limit of infinite dilution. These frequencies are 1342.7 ± 0.1 cm −1 for N 3 − and 1047.4 ± 0.1 cm −1 for NO 3 − . When Li + or Na + was present in solution with the azide anion, the ν 1 frequency was shifted to a higher value than the infinite dilution frequency, with both cations having approximately the same effect, whereas when K + , Rb + or Cs + was present the ν 1 frequency was decreased, the largest decrease being caused by Cs + , followed by Rb + , with the smallest decrease being caused by K + . In the case of the nitrate anion, the cations Na + , K + , Li + and Rb + were all responsible for an increase in the NO 3 − ν 1 frequency with respect to the infinite dilution value, with the magnitude of the perturbation decreasing from Na + to Rb + . When Cs + was present the NO 3 − ν 1 frequency was observed to decrease by a very small amount. It is suggested that for the vibrationally excited azide anion, the cation perturbation occurs through a form of polarizability interaction. However, the cation‐nitrate anion interaction is thought to occur through the effect that the hydrated cation has on the vibrationally excited nitrate anion cosphere of hydration.