  Many samples of current interest in molecular physics and physical chemistry
exist in the liquid phase and are vaporized for the use in gas cells, diffuse
gas targets or molecular gas jets. For some of these techniques the large
sample consumption is a limiting factor. When rare, expensive molecules, such
as chiral molecules or species with isotopic labels are used, wasting them in
the exhaust line of the pumps is a quite expensive and inefficient approach.
Therefore, we developed a closed-loop recycling system for molecules with vapor
pressures below atmospheric pressure. Once filled, only a few valves have to be
opened or closed and a cold trap must be moved. The recycling efficiency per
turn exceeds 95 %.
