Woodcox, M.
, Evans, S.
, Bone, R.
, Mattes, S.
, Mahata, A.
, Hagerstrom, A.
, Muzny, C.
, Sundararaman, R.
, Schwarz, K.
and Stelson, A.
(2025),
Detecting ion pairing in sodium halide solutions with dielectric spectroscopy, The Journal of Chemical Physics, [online], https://doi.org/10.1063/5.0272934, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=959517
(Accessed September 16, 2025)
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Detecting ion pairing in sodium halide solutions with dielectric spectroscopy
Published
Author(s)
, , , Spencer Mattes, Avik Mahata, , , Ravishankar Sundararaman, ,
Abstract
The dielectric response of an ionic solution is determined by the diffusion of ions in solution, the response of solvent molecules and the intermolecular interactions between solvent, cations and anions. While the ionic diffusion and solvent responses are large signals in the dielectric spectra, the contributions of the ion-ion and ion-water interactions can be difficult to measure and compute. Here, we combine computational and experimental techniques to investigate the impact of ion-ion and ion-water interactions in aqueous sodium halide solutions. Our molecular dynamics simulations directly apply an electric field to solutions and compute the dielectric response from the polarization to isolate the effects of individual species contributions. We supplement this approach with broadband microwave microfluidic spectroscopy measurements to measure the response of sodium fluoride solutions. Both computed and measured spectra support the existence of a Debye relaxation due to ion pairs in solution. Additionally, our computed spectra show a small ion-ion contribution for NaCl and NaF to the dielectric spectra that is negative in magnitude and does not correspond to a typical Debye relaxation. Our measured spectra support the conclusions of the computed spectra to within the measurement uncertainties.Citation
The Journal of Chemical Physics
Volume
163
Issue
1
Pub Type
Journals
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Created July 1, 2025, Updated September 6, 2025