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Raman scattering from YbAlG and YbGaG at 80 K was investigated in order to obtain reliable crystal field levels of the Yb3+(2F7/2) ground manifold. Our 2F7/2 assignments for YbGaG (0, 546, 610, and 624 cm−1) are complete (four levels predicted for D2 site symmetry) and are consistent with the levels determined from absorption by Buchanan et al. [Phys. Rev. 159, 245 (1967)]. For YbAlG our assignments (0, 587, 621 cm−1, and a doublet at 758 cm−1) differ significantly from the work of Buchanan et al. who may have adopted the wrong assignments due to numerous vibronic side bands present in their original absorption spectra. Further confirmation of our results for YbAlG was provided by a companion study of LuAlG because of its closed 4f shell (no electronic scattering) and the nearly identical masses of Lu and Yb (i.e., equivalent phonon spectrum).

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This paper reviews the characteristics of a high pressure ionization gauge originally reported by Schulz and Phelps [Rev. Sci. Instrum. 28, lOSt (1957)]. The gauge is available commercially as the Westinghouse WL-7903. A brief theoretical treatment is given for the linear regime, p$t Torr. The gauge sensitivity is derived from known ionization cross sections for a number of atomic and molecular gases, including argon, krypton, and xenon. Also, an improved gauge controller circuit is described. For a given gas the controller normalizes the gauge sensitivity to unity and provides a direct reading of gas pressure on a linear scale. The controller has proved very useful in the operation of a cw :Bowing-gas laser in which 0.1 to 300 mTorr pressures occur. In addition, new experimental data are presented for argon, krypton, nitrogen, and air in the "nonlinear" range 2-500 Torr.