The density dependences of the nitrogen hyperfine coupling constant (a N) and line width (ΔHpp) of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) free radical have been investigated at near-infinite dilution in gaseous and supercritical carbon dioxide using steady-state EPR spectroscopy. The local density augmentation around the radical is quantified based on the density dependences of the a N. The viscosity dependences of the ΔHpp are reproduced by the modified Stokes-Einstein equation, suggesting the local solute-fluid density augmentation.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry