Abstract
By analysing the temporal current shapes of electron avalanches the different secondary ionisation processes occuring in H2- and O2-discharges have been separated and data taken. In hydrogen at E/p < 250 volts/cm Torr secondary electrons are released at the cathode by photons emitted mainly from excited states of the WERNER-bands of the H2-molecule. In oxygen secondary electrons are released both within the gas and at the cathode at E/p < 500 volts/cm Torr by photons from electronic states above the first ionisation level of the O2-molecule, which are excited by single electron collisions. With increasing E/p additional secondary electrons in hydrogen are produced by positive ions at the cathode, but for E/p > 170 volts/cm Torr the avalanche currents cannot be interpreted by the photon and ion processes thus indicating the action of a third mechanism. The same result was obtained for oxygen at E/p > several 100 volts/cm Torr. This additional process is discussed on the basis of different ion species and a possible action of fast neutral molecules resulting from charge exchange collisions.

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