Apparent cross sections for metastable ion production by electron impact

Fractions of long-lived excited species in noble-gas ion beams which were produced by various methods have been determined by virtue of slow ion impact induced electron emission from clean polycrystalline tungsten. Investigations with ion beams produced by single electron impact on atoms permitted the determination of cross sections for the production of singly charged metastable ions of the noble gases Ar, Kr and Xe. The cross sections obtained increase steeply from threshold up to their maximum values of about 10 -17 cm 2 within 1.5 time threshold energy. Processes responsible for production of these metastable ions are discussed and the method applied is compared with other techniques for metastable ion detection.