Figure illustrates the dependence of ionic conductivity on cation species in 0.01 M MCl aqueous electrolyte solutions (M = Li, Na, K, Rb, and Cs). Notably, the modulation of ionic conductivity varies with the cation species. For instance, the bulk ionic conductivity of LiCl (0.11 S m-1) is comparable to the ionic conductivity of LiCl in a cavity (0.14 S m-1). On the other hand, the ionic conductivity of CsCl in a cavity (0.41 S m-1) is three times higher than the bulk ionic conductivity of CsCl (0.15 S m-1). In any case, the highest ionic conductivity was observed at a cavity length of approximately 3.3 µm, which corresponds to the coupling of the third-order cavity mode with the O-H stretching mode. This suggests that the coupling of the OH stretching mode of water enhances the ionic conductivity.