Letter | Published:

Pressure Differences in a Direct-Current Capillary Discharge

Naturevolume 191pages265266 (1961) | Download Citation



THIS communication deals with the difference of pressure which arises between the ends of the capillary of a d.c.-excited krypton discharge lamp as a result of the motion of ions and electrons in the electric fields1 of the discharge. The effect is of importance in view of the adoption of the 0.606µ line emitted by krypton-86 as the new standard of length2. The wave-length of this line can be shifted, because of broadening due to pressure, by an amount which depends on the pressure and the current in the discharge; this shift is of the order of one part in 108 under the conditions for excitation by means of a d.c. discharge, which have been recommended by the International Committee of Weights and Measures3.

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  1. 1

    Francis, G., Handbuch der Physik., 22, 195 (Springer, 1956).

  2. 2

    General Conference of Weights and Measures, Paris, October 1960.

  3. 3

    Proc. Verb. du CIPM, 27 (1960).

  4. 4

    Meihuizen, J. J., Dampspanuingen en Vloeistof-en Dampdichthenden van Krypton (Leyden, 1940). See also Fisher, B. B., and McMillen, W. G., J. Phys. chem., 62, 494 (1958).

  5. 5

    Baird, K. M., and Smith, D. S., Canad. J. Phys., 37, 832 (1959).

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  1. Division of Applied Physics, National Research Council, Ottawa

    • D. S. SMITH


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