Enhancing He 2 ³S₁ state production in the burst regime of a nanosecond discharge

Abstract Atmospheric repetitive He discharge with 10 ns current peak width working in the burst pulse regime was studied. The production of He 3 S 1 and 1 S 0 metastable states was examined using laser- collisions- induced fluorescence and atomic absorption spectroscopy. Both methods independently reveal a significant increase of 3 S 1 population in the burst regime, depending on the plasma pulse separation time in the burst. Up to a seven-fold increase in the 3 S 1 population was detected after the third pulse in a 3-pulse burst sequence (as compared to the value obtained after the first pulse or in a single pulse regime), not requiring additional applied power. The observed effect is explained by recombination between the electrons and the ground state ions (He + , He <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> ) produced in the previous plasma pulse and refilling the volume of interest in few hundred µ s.