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Voltage-breakdown curves in a Ne+0.1% Ar Penning mixture for insulated-electrode discharges are strongly influenced by changes in the surface properties of a deposited MgO cathode. A model has been developed to calculate an effective secondary-electron-emission coefficient γ in Penning mixtures as a function of the insulator-energy-band parameters. Incorporation of the calculated γ into the breakdown criterion results in good agreement between calculated and measured voltage-breakdown curves for differently prepared MgO cathode surfaces. The calculated results show that the value of γ for argon ions depends on the state of the MgO surface, and this occurs through a change in the width of the band gap of MgO. The results also show that a nonzero value of γ (Ar+) significantly lowers the breakdown voltages and changes the shape of the breakdown curves at higher values of P0d.

Associative ionization in thermal energy (300 K) collisions between Ne(2p 5 3s 3P2), Ar(3p 5 4s 3P2) metastable atoms and hydrogen atoms H(ls 2S1/2) has been studied by high resolution (20 meV) electron spectrometry. The spectra exhibit structure due to the formation of different vibrational states in the molecular ion and show superimposed rotational structure. Direct information is obtained on the relative population of the rovibronic states and on their energy positions. The well depth of the ionic potential curves has been determined as : D e (Ne H + X 1 X +) = 2.27 (3) eV, D e (Ar H + X 1 X +) =4.02(3) eV.