Laser-induced current in air gap at atmospheric pressure

Current pulses induced by pulsed laser radiation at a metal target were studied at radiation intensities below thresholds for laser ablation. Measurements were made in air in weak dc fields where ionization by electron impact does not occur. Current pulses as a function of radiation intensity were recorded. Experimental conditions allowed a distinction between charged particles injected into the gap from the target electrode and those created in the gas medium. With the intensity growth, the increase in the number of target-injected charge carriers stops and gas-created particles make a large contribution to the total current. Modelled current pulses correspond to those recorded in the experiment. Furthermore, the modelling verifies that the space charge of negative ions controls the current of target-injected charge carriers.