Cover: Journal of the Chinese Chemical Society 6/2018

This invited review summarizes the long way from the idea to attach a helium atom to cold molecular ions as sensor to its routine use in cryogenic rf ion traps. In the last 25 years, He buffer gas cooling became a very efficient and rather general method for getting all internal degrees of freedom into equilibrium with the cold bath gas. Using, in addition, ion traps, low enough temperatures, and high enough densities, He–M⁺ complexes can be formed now routinely from all kind of mass selected M⁺ ions. These techniques opened up many possibilities for studying the structure and reactivity of charged objects. Meanwhile vibrational predissociation spectroscopy in the fingerprint region has evolved as a routine method in analytical chemistry. More details will be discussed by Dr. Dieter Gerlich on page 629~801 in this issue.