Lowâ€frequency (<300 cm−1) vibrational interactions between gold surfaces and dissolved halides in water were investigated by surfaceâ€enhanced Raman spectroscopy (SERS). Experiments with NaF, NaCl, NaBr, and NaI salts indicate that the Raman shifts of the Auâ€X− SERS bands correlate with the bond strength of the corresponding covalent interaction. These lowâ€frequency SERS bands open up new means to investigate the aggregation of nanoparticles in aqueous environments.