The vacuum wavelengths of 27 lines of Hg<sup>198</sup> and 6 lines of Kr<sup>86</sup>have been measured relative to the international standard of length, the Kr<sup>86</sup> line at 6057.80211 Å, by photographic Fabry-Perot interferometry. These measurements were made with Hg<sup>198</sup> electrodeless lamps containing argon at pressures of ¼, 3, and 10 mm Hg and a Kr<sup>86</sup> hot-cathode lamp operated according to the conditions prescribed by the International Conference on Weights and Measures in 1960. Energy-level values have been derived from the wavelengths of each of the Hg<sup>198</sup> sources, and on the basis of these values, the energy level and wavelength shifts per unit pressure of argon have been calculated. The suitability of the Hg<sup>198</sup> electrodeless lamp as a source of wavelength standards for interferometric measurement of length and wavelength is discussed.
VICTOR KAUFMAN, "Wavelengths, Energy Levels, and Pressure Shifts in Mercury 198," J. Opt. Soc. Am. 52, 866-870 (1962)