To summarize the above IR analyses of the various systems, we can corroborate the correlation between decreasing O-H frequency and increasing intensity with increasing water content of the clusters, which is gradually reversed when adding ions to the system. Finally, we see a propensity toward red-shifting of the O-H vibrational frequencies when adding more ions to the hydrated PA clusters even though the O-H frequencies in the (PA) 1 (Na + ) 1 (w) 0-5 clusters resonate consistently above 3000 cm -1 .