Detecting ion pairing in sodium fluoride solutions with dielectric spectroscopy

M Woodcox and SR Evans and AM Hagerstrom and RA Bone and NR Jungwirth and S Mattes and A Mahata and ND Orloff and C Muzny and JC Booth and KA Schwarz and AC Stelson, JOURNAL OF CHEMICAL PHYSICS, 163, 014303 (2025).

DOI: 10.1063/5.0272934

The dielectric response of an ionic solution includes ionic diffusion, solvent molecule reorientation, and the intermolecular interactions between solvent, cations, and anions. While ionic diffusion and solvent reorientation produce large responses 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 fluoride solutions and determine whether an ion pairing peak exists in the dielectric spectra. We use our recently developed direct electric field approach to perform frequency- resolved configurational analysis of ion pairing. From this analysis, we identify a Debye peak associated with the reorientation of ion pairs. Our broadband microwave microfluidic spectra of sodium fluoride solutions further support the existence of a low-frequency Debye relaxation due to ion pairs in the solution.

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