Determination of atomic hydrogen density by Lyman-alpha laser fluorescence spectroscopy

Atomic hydrogen densities and their detection limit were determined accurately by vacuum ultraviolet laser fluorescence spectroscopy, tuned to the Lyman alpha line, using the third harmonic generation of a tunable dye laser pumped by a XeCl excimer laser as the excitation source. A well-characterized atomic hydrogen source, whose absolute density was measured by absorption, was used to assess the detection capability of the laser fluorescence spectroscopy, which gave absolute density determinations to within +-30 % and a detection limit of 3 x 1015 m-3. (author)