Figure 19.

FFT-IR spectra of water (blue line) and 4 M HCl (red line) with assignments of the different spectral regions to different structures of the solvated proton (cartoons). The vibrational modes shaded in green involve the excess proton (purple color), whereas the vibrations in bulk/flanking water molecules are shaded in red. Details of the assignments are discussed in the text. Reproduced from ref 99 with permission. Copyright 2015 American Association for the Advancement of Science