The combination of a widely tunable infrared laser source with tandem mass spectrometry enables the routine recording of IR spectra of gaseous molecular ions. With the aid of theoretically predicted vibrational spectra, these IR spectra can be used to derive molecular structure information on the ionized species. As an example, the sites of protonation, deprotonation or metal ion attachment in a molecule can be accurately determined using “infrared ion spectroscopy” (IRIS).
Electrolytes respond to contact with a charged solid surface (metal electrode, semiconductor or insulating ionic solids) by formation of an electric double layer. The modelling of electric double layers at an atomistic level remains a major challenge. A well known technical problem is of course how to fit models of electric double layers in the periodic cells commonly used in atomistic simulation. However, there remain even open questions of a more fundamental nature.