Collisional quenching of metastable hydrogen

Absolute total cross sections for collisional destruction of metastable hydrogen H(2S) in collisions with argon, nitrogen and water vapour have been measured for energies between 2 and 60 kev. Low-energy data were also obtained for metastable deuterium. For all three target gases the cross sections rise from about 0·5 × 10 -15 cm 2 at 60 kev to 2·5 × 10 -15 cm 2 at 2 kev. Special attention was paid to the precise determination of the target gas pressure and the effective target length. The procedure is discussed in some detail. As the results of this work are absolute, they may be of some interest in connection with the design and operation of polarized negative hydrogen ion sources.