β Scribed by A. Michels; H. Tjin A Djie; H. de Kluiver; C.A. Ten Seldam
No coin nor oath required. For personal study only.
In a high pressure discharge cell direct current arcs have been investigated in hydrogen and heliumcompressed up to 1000 atmospheres. For helium, the current, the voltage across the arc and its diameter have been measured as a function of pressure. From these data the temperature in the positive column was calculated with the assumption that the Saha equation is valid under the experimental conditions. For hydrogen, preliminary experiments also yielded an estimate of the temperature. Photographic analyses of the spectra of H2 and He have been made. As some H2 was present in the He used, it was also possible to observe the effect of high density He on the H2 spectrum. Finally, the total intensity of the helium arc in the range 4000--6500 A was determined photoelectrically as a function of pressure. Β§ 1. Introduction. In order to check the predictions made on the basis of the atom-in-box model 1) 2) it was considered desirable to investigate the spectra of hydrogen and helium at high pressures. It would have been preferable to measure the absorption spectra of helium and atomic hydrogen, as these measurements can, in principle, be carried out at equilibrium conditions. This is impossible, however, for several reasons. At low temperatures, electronic transitions occur only i~n the Lyman series; the strong absorption in this region necessitates the use of thin layers and the techniques of vacuum spectroscopy. Observations of the Balmer lines are possible only at very high temperatures. Investigation of the spectrum of atomic hydrogen is complicated by the necessity of dissociating the hydrogen molecules.
Under these circumstances it was decided, in spite of the complications involved, to investigate the emission spectra of arc discharges in helium and hydrogen. The Balmer lines appear in this case because of the high temperature; these lines lie in the visible region.
The experiments were performed at such low current densities, that the Stark effect was overshadowed by other disturbing factors. In addition to the optical properties of the helium arc, the electrical characteristics have also been determined. The latter observations partly overlapped the similar
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Large pressure gradients and unrecognizable variations of pressure occur when solid substances are compressed by cold anvils (pistons) and heated by internal heaters. To improve the reliability of the results the miniaturization of samples and preliminary firing of pyrophyllite (which transmits pres