Preparation of Spin Polarized Metastable Atoms

A helium discharge source produces a beam which contains ground-state He(l S) atoms, metastable He(2 S) and He(2 5) atoms (He ) as well as long-lived Rydberg atoms. The radiative lifetime of the He(2 5) atoms of about 10 s [15] is infinitely long compared with the millisecond flight time between source and detector. 

A subsequent sextupole magnet (the magnetic arrangement is given in Fig. 2.9) acts as a polarizer by preferentially transmitting the atoms with a magnetic 

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