The high-temperature equilibrium concentration of the gaseous species and of the deposited glass formed by the oxidation of the chlorides of silicon and germanium was measured and compared with thermodynamic calculations. The equilibrium incorporation of germanium in phosphate-silicate particles formed from the gas at ~1 6 5 0 K is shown to form a theoretical basis from which the actual composition of completed preforms and optical fibers made by the modified chemical vapor deposition process can be calculated. The efficiency of incorporation of germanium dioxide in the silica glass system is determined as a function of the oxygen concentration and the ratio of germanium to silicon. The recently redeveloped element potential method is used to minimize the Gibbs energy of the system and obtain the temperature and compositional dependences. The agreement of calculated and experimental results obtained in this work suggests a broad spectrum of uses of the method for understanding and calculating chemical reactions. The method is exceptionally well suited for applications where the determination of species concentrations for multiphase processes is desired over broad ranges of concentrations, temperatures, and pressures.
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.
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