Detection of atomic hydrogen and deuterium by resonant three-photon ionization

Abstract
Resonantly enhanced three‐photon ionization spectroscopy is employed for the detection of ground‐state atomic hydrogen and deuterium. Concentrations as low as 4×109 atoms/cm3 in the presence of 1017 atoms/cm3 of buffer gas are detected with an implicit time resolution of less than 10 nsec. A useful dynamic range of at least 4×104 is demonstrated and saturation of the ionization in a 2×10−4‐cm3 focal volume is observed. The presence of H can easily be distinguished from that of D and the three‐dimensional spatial distribution of H or D can be determined.