Our numerical results obtained for NaCl slit pores show a strong dispersion of T 1 for frequency ν ∈ [3 -100] MHz only when c s > 0 (Fig. , Fig. ). For Na 2 SO 4 , such T 1 dispersion is reported for all the values of c s considered, including c s = 0, with a degree of dispersion that increases with c s . The frequency range ν ∈ [3 -100] MHz corresponds to events of duration larger t > 10 ns, i.e., much larger than the characteristic molecular times. For instance the typical rotation time τ R of water molecules at the solid walls never exceeds 20 ps (Fig. ), and the typical adsorption time τ A never exceeds 100 ps (Fig. ). On the other hand, the maximum characteristic diffusion time of a water molecule in between two adsorption/desorption events is t D ≈ h 2 /D ≈ 30 ns where D = 2 • 10 9 m 2 /s is the diffusion coefficient of water, and h ≈ 7 nm the pore size. Therefore those adsorption-desorption events are likely to be at the origin of the dispersion of T 1 for ν ∈ [3 -100] MHz. This assumption is consistent with the Levitz model, for which the surface relaxation time in Eq. ( ) is associated to a 'slow' contribution induced by successive adsorption and relocation steps of the fluid molecules inside the pore . Strikingly, for NaCl slit pores with h ≈ 7 nm and c s = 0, no such low frequency regime is observed (T 1 is flat for ν < 100 MHz, Fig. ) while alternative adsorption-diffusions steps are present, with a typical adsorption time τ A ≈ 55 ps. Here, we suggest that the absence of low frequency regime for NaCl pores with c s = 0 could be due to the relatively weak interaction between crystal NaCl(100) surface and water, as seen by the absence of strong polarization of the water molecules at the solid surface 5).