Vibrational predissociation spectroscopy and theory of Ar-tagged, protonated Imidazole (Im) Im1-3H+·Ar clusters

► Ar-tagged vibrational spectra of Im1-3H+. ► Parallel stretching mode of the shared H+ in Im2H+ appears as doublet around 1000 cm−1. ► Bands reveal symmetrical charge concentration on central imidazolium in Im3H+.