title: Saturation of three-photon ionization of atomic hydrogen and deuterium at 243 nm.
abstract: Two-photon-resonant, three-photon ionization of atomic hydrogen and deuterium is performed at 243 nm, and the ions are detected by time-of-flight mass spectrometry. The power dependence of the 1S-2S two-photon excitation and one-photon ionization of 2S hydrogen and deuterium are determined. The ionization step saturates at 4 x 10(6) W/cm(2). The two-photon step-power dependence varies with laser linewidth, with saturation occurring between 1 x 10(7) and 3 x 10(7) W/cm(2). The extraction electric field in the mass spectrometer does not affect the 2S excitation. Strong signals are recorded at atomic concentrations of 10(5) atoms/cm(3). Nonresonant ionization of background gases producing H(+) and D(+) is minimized.
authors.forename: S W
authors.initials: SW
authors.lastname: Downey
authors.forename: R S
authors.initials: RS
authors.lastname: Hozack