Observation of light-induced current in a plasma of a microwave discharge in a mixture of Ar with lithium vapors resonantly excited by laser radiation

Experimental observation of light-induced current in a plasma of a microwav e discharge in a mixture of argon with atomic lithium vapors is reported. L ithium atoms were excited by laser radiation whose frequency was close to t he frequency of the resonant absorption line. The magnitude of electric cur rent reached 4.9 x 10(-9) A. The specific dependence of the signal of light -induced current can be explained only under the assumption that the Pennin g ionization of lithium by metastable argon atoms is the dominant ionizatio n mechanism. This statement is supported by the magnitude of the effect. It was an order of magnitude greater than the value that might be provided by direct ionization by electron impact.