The Local Vibrational Mode Theory and Its Place in the Vibrational Spectroscopy Arena.

This Feature Article starts highlighting some recent experimental and theoretical advances in the field of IR and Raman spectroscopy, giving a taste of the breadth and dynamics of this striving field. The local mode theory is then reviewed, showing how local vibrational modes are derived from fundamental normal modes. New features are introduced that add to current theoretical efforts: (i) a unique measure of bond strength based on local mode force constants ranging from bonding in single molecules in different environments to bonding in periodic systems and crystals and (ii) a new way to interpret vibrational spectra by pinpointing and probing interactions between particular bond stretching contributions to the normal modes.