In situ diagnostics in plasmas of electronic-ground-state hydrogen molecules in high vibrational and rotational states by laser-induced fluorescence with vacuum-ultraviolet radiation

Detection of excited electronic-ground-state hydrogen molecules with upsilo n " up to 13 ill a magnetic multipole plasma source was performed for the f irst time by laser-induced fluorescence with vacuum-ultraviolet radiation. The measurements are taken after fast shutoff of the discharge current. The rovibrationally excited molecules live longer than the plasma background l ight so that the fluorescence light can be detected with good signal-to-noi se ratio. Absolute level populations are measured as well as decay times. T he theoretically predicted suprathermal population of the vibrational distr ibution is clearly identified. The H- density is calculated on the basis of the measured populations and the measured electron energy distribution fun ction. It is in excellent agreement with the H- density measured by photode tachment.