Redetermination of cross sections for formation of metastable He+(2s) ions in fast collisions using an improved calibration procedure

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Abstract
A photoionization chamber has been used to determine the absolute intensity of 304 AA radiation emitted during electric-field quenching of fast He+(2s) metastable ions. The measurements have been used to redetermine with greatly improved accuracy cross sections previously measured in this laboratory for formation of He+(2s) metastable ions by (a) one-electron capture in the passage of 10-60 keV 3He2+ ions through H, H2, He, Ar, Kr, K, N2 and O2 and (b) direct excitation of 6-30 keV 3He+ ions in passage through He, Ar, Kr, H2, N2 and O2. The measurements show that, while relative cross sections for the different target gases remain unchanged, previously estimated absolute values should be increased by a factor of 2.2. Cross sections revised in this way are believed to be accurate to within 15% for H2 and 20% for the other target gases.