Density Distributions of H and H₂ in Pulsed Microwave Hydrogen Plasmas

Temporal distribution of the H atom and H₂ densities in a pulsed microwave hydrogen plasmas has been measured simultaneously by two-photon absorption laser-induced fluorescence (TALIF). The measurement of the H-atom absolute density obtained by NO₂ titration in a flow tube reactor shows that the density of H₂ could be determined by the measured effective lifetime of the TALIF signal via the quenching equation. The H-atom density of about 1.5 x 10¹⁵cm^-3 in both pulsed and stationary phases does not obviously change. It is found that the gas temperature volume effect plays an important role in governing the distributions of the H-atom density and it is mole fraction. The calculated gas temperature is in good consistent with the rotational temperature of H₂ measured by optical emission spectroscopy in pulsed phase.