This setup enables to separate nuclear spin isomers of water in a supersonic molecular beam using a magnetic focalisation technique.The continuous molecular beam is produced from the supersonic expansion of water vapour seeded in argon carrier gas. Ce center of the jet is collected using a skimmer to enter the delection zone after two stages if differential pumping. Water molecules in the ortho nuclear spin state (I=1) interact with a strong magnetic gradient produced by a serie of hexapolar magnets enabling the focalisation of the molecules having MI=-1 sublevel, when molecules having MI=+1 are deflected and molecules in the sublevel MI=0, that is ortho and para states, do not change trajectories.The characterisation of this ortho-enriched molecular beam is directly done in the molecular beam using REMPI (2+1) spectroscopy coupled with a time-of-flight mass spectrometer.
A few photos illustrating our setup:
View of the setup in the lab 
The expansion source chamber at the front 
Detail of the cryopump in the expansion chamber 
The end of the magnetic lens 
The analysis chamber 
The time-of-flight mass spectrometer (left) and the micro-channel plates detector (right) 
Detail of the molybdenum grid on the TOF electrodes 
The primary pumping is done with scroll pumps (left) and helium compressor (right) cools the cryostat
