Fast Diffusion of the Cl- Ion in the Headgroup Region of an Oppositely Charged Micelle. A 35Cl NMR Spin Relaxation Study

Field-dependent 35 Cl spin relaxation rates have been measured in the micellar solution of C 16 TACl−D 2 O. The data are analyzed in terms of a fast hydration dynamics of the ion and a slower motion that consists of ion diffusion and micellar tumbling. This model provides a distinct motional correlation time of the Cl - ion from which it is concluded that, on the nanosecond time scale, the Cl - ion diffuses on the micellar surface close to its bulk diffusion speed. The hydration dynamics on the picosecond time scale differs from that in a dilute solution. These features are similar to that observed for Br - ions in the vicinity of aqueous micelles of C 16 TABr (Hedin, N.; Furó, I. J. Phys. Chem. B 1999, 103, 9640).