Flowing afterglow

An ion source immersed in a flow of helium or other inert buffer gas that carries the ions through a meter-long reactor at pressures around 100 Pa.

a reactor for observing ion-molecule reactions, in which ions are introduced to a bath gas containing a neutral reactant, and flowing rapidly down a vacuum system, where neutral pressure and distance become the reaction variables. Detection of the ions is by mass spectrometry through a leak at the product end of the system.