Resonance Ionization of Atomic Hydrogen and Deuterium.

Two-photon resonant, three-photon ionization of atomic hydrogen and deuterium is performed using single-color excitation. The conditions for nearly 100% ionization of the ground-state atomic population are determined, and are in good agreement with theoretical predictions. Relatively large sample volumes can be probed, with resultant good sensitivity. Strong signals are recorded at atomic concentrations of about 1 x 10 sup 5 atoms cm sup (-3) (3 x 10 sup (-12) Torr partial pressure). Thus this technique will be applicable for use in post-ionization sputtered neutral mass spectroscopy (SNMS) in achieving detection limits near the parts-per-billion level in solids. Nonresonant ionization of background gases resulting in H sup + and D sup + formation is minimized, and could obviate the need to use D in place of H in many applications where the background gas limits the detection sensitivity for H in conventional secondary ionization mass spectroscopy (SIMS) analyses.