Dynamics of the formation of excited hydrogen, H(n=2,3,4), during a pulse discharge in methane

The dynamics of the formation and decay of excited hydrogen during a pulse discharge in methane at a pressure of 200 Pa and energy density of 0.05 J/cm{sup 3} has been studied. The population of hydrogen in the n = 2 state was monitored by the laser absorption method. The time constant of the decay of the excited hydrogen was measured to be 95 {plus minus} 15 ns. The concentration of free electrons reached a maximum value of 7 {times} 10{sup 14} cm{sup {minus}3}, and the time constant of their recombination was 220 {plus minus} 50 ns. The formation of appreciable amounts of atomic hydrogen in the ground state during the discharge, H(n = 1) > 10{sup 16} cm{sup {minus}3}, was estimated on the basis of a kinetic model.