K. W. Meissner

Improved Cu ii Standard Wavelengths in the Vacuum Ultraviolet

Interferometric wavelength measurements of sixty-one copper spark lines in the region 2884 A to 1979 A have been carried out by means of a Fabry-Perot interferometer equipped with 4, 12, and 20 mm spacers. The light source used was a water-cooled hollow cathode Schuler tube operated principally with circulating helium but occasionally with circulating neon.The measurements were employed to establish the 4s and 5s even levels and 4p odd levels of Cu ii. After fixing these low levels, their values were combined with the grating measurements of Carter and Shenstone to establish the values of certain higher odd and even levels. Use was then made of the Ritz combination principle to calculate precise wavelength values of approximately sixty copper lines in the region between 1663 A and 984 A with estimated accuracies which varied from ±0.0003 A to ±0.001 A.

Arc Spectrum of Germanium

The arc spectrum of germanium has been investigated in the region 1546 A to 11 252 A with concave grating spectrographs and interferometers by the use of various arc and hollow cathode sources. Wavelength measurements supplied by other laboratories are included. The wavelength material has been greatly improved and extended from 184 lines to 475 lines. Of these about 200 visible and infrared lines were found by the development of a special low pressure Ge arc source.An extended analysis of this spectrum has led to 94 new levels and nearly 300 newly classified lines. At present there are 68 even levels belonging to the 4s2 4pnp and 4s2 4pnf configurations and 87 odd levels belonging to the 4s2 4pns, 4s2 4pnd, and 4s4p3 configurations. Improved series limit calculations give the value 63 715±10 cm−1 for the 4s2 4pP212° level of Ge II with respect to the 4s2 4p2 3P0 level of Ge I, corresponding to an ionization potential of 7.899±0.001 volt.

Germanium Standard Wavelengths in the Vacuum Ultraviolet

The Ge I lines proposed by Meissner, VanVeld, and Andrew as standards in the vacuum ultraviolet have been investigated with respect to their usefulness as standards. After elimination of nine lines not fit for the purpose there remain 75 lines which can serve as auxiliary standards. These standards were employed for obtaining improved wavelengths in the spectra of Ge I, Ge II, and Ne II. For Ge II improved level values were derived from this measurement which also revealed that the term 8f2F05/2,7/2 is inverted.

New Germanium Standard Wavelengths in the Region from 1998 A to 1630 A

The application of interferometric and grating measurements in the long wavelength region of the germanium arc spectrum in connection with the extended analysis of this spectrum permits the calculation of precise wavelengths of 69 Ge i lines in the vacuum ultraviolet region on the basis of Ritz’s combination principle. This furnishes a welcome enrichment and extension of the list of Ge i vacuum ultraviolet standards obtained by VanVeld and Meissner on the same basis by the use of precision measurements in the short wavelength region. Most of these lines can be recommended as reliable secondary standards in the vacuum region.

Mercury Atomic Beam Lamp

The construction and operation of a simple atomic beam source employing natural mercury is described. Lines of great sharpness are obtained when the emitting beam is viewed perpendicularly to the direction of the flight of the atoms. The Hg198 component of the line 2537 A is isolated from the other components by proper selection of the interferometer spacer so that it can be compared with the same line of the Hg198 Meggers lamp. This comparison shows that the atomic beam line is much sharper and that it is feasible to construct an atomic beam lamp employing a single even isotope of mercury.

Interference at Great Retardations Obtained with a Calcium Atomic Beam Source

By employing a calcium atomic beam source in emission and by using a beam of high collimation very clear Fabry-Perot patterns of the resonance line of calcium, λ4226 A, were obtained with retardations of 60, 78, 94, 108, 120, and 130 cm. The corresponding order numbers are about 1.42, 1.85, 2.22, 2.56, 2.84, and 3.08 million and greatly surpass those obtainable with the best conventional cooled source available at present. The good definition of the fringes obtained with the retardation of 130 cm suggests that the limit of interference is considerably higher.

The Fine Structure of the ( 4 S°)3p 3 P Term of Oxygen O I*

The fine structure of the (4S°)3p3P term of O I has been determined by interferometric measurement of three triplets at 8446A, 7245A, and 6046A. The term is found to be partially inverted in agreement with Edlen’s findings.

5 S 2 ° Term of Neutral Germanium*

The discovery of two new germanium lines at λ 2467.368 A and λ 2416.505 A led to the recognition of the missing 4s4p3 5S2° the S2° term of Ge i. It is situated 41 926.726 cm−1 above the ground level 4s4p2 3P0 and the lines mentioned above are the combinations ν=4s24p2 3P2,1,–4s4p3 5S2°, respectively.

Calcium Atomic Beam Source and Interference beyond Two-Meter Retardation*

Fabry-Perot interference patterns of the resonance line of calcium, λ4226 A, have now been obtained at retardations of 153 and 204 cm by employing a highly collimated calcium atomic beam source in emission. The corresponding order numbers are 3.62 and 4.82 million. The appearance of these fringes suggests that the half-width of the line is less than 3×10−3 cm−1 which is one-fourth that of the proposed primary standard of length and one-tenth that of the present primary standard of wavelength. The use of an atomic beam source for the production of the length standard is discussed.

Selection of Optimal Spacers in Perot-Fabry Interferometry*

The paper contains a general discussion of the conditions for optimal separation of Perot-Fabry patterns. A convenient graphical method is given which permits the selection of the proper spacer thicknesses for the clear resolution of the components of a pattern even in complicated cases.