Surface recombination of hydrogen atoms studied by a pulsed plasma excitation technique

The H atom lifetime in a low pressure hydrogen microwave plasma was measure d using a pulse induced fluorescence technique. This technique is compared to results obtained by a laser spectroscopy technique. We first demonstrate the validity of the method and then deduce H atom lifetime pressure depend ence. The H atom surface loss probability on fused silica was also deduced from our measurements. We show that this coefficient is not constant in the time afterglow but decreases almost by one order of magnitude (from 2.3 x 10(-3) to 2.1 x 10(-4)) during the first milliseconds. These results are ex plained using recent experimental and theoretical works concerning atom-sur face interaction in low temperature plasmas. (C) 2001 American Institute of Physics.