Possibility of a surface electrical discharge associated with optical breakdown at the surface

The possibility of a surface electrical discharge developing due to the contact potential difference between a laser plasma and a conducting surface is considered. The plasma cloud which forms in the laser spot plays the role of a voltage source. The typical radius over which the discharge spreads is calculated and it is shown that the effect has a pressure threshold. The superheating of gas in the layer of thermionic emission electrons which forms at the surface when the latter is heated by laser radiation is proposed as a mechanism for the initial plasma formation. 11 refs