The Continuous Absorption of Oxygen Between 1750 and 1300A and Its Bearing Upon the Dispersion

In connection with recent measurements of the dispersion of oxygen down to 1920A, the continuous absorption of oxygen between 1750 and 1300A has been investigated quantitatively with a small fluorite spectrograph by the photographic-photometric method. The results are given in a graph, which shows that the absorption co-efficient $\alpha$ as function of the wave number $\nu$ has a relatively sharp maximum at 6.8×${10}^4$ ${\mathrm{cm}}^{-1\mathrm{}}$ ($\lambda =1450\mathrm{}\mathrm{A}$) and falls off rather symmetrically on both sides. The maximum absorption coefficient reduced to N.P.T. is about 490 ${\mathrm{cm}}^{-1\mathrm{}}$. The absorption in this region of the spectrum is so strong that during a few minutes exposure a great part of the oxygen disappears, being dissociated and probably absorbed by the metal walls of the tube. By integration of the absorption curve one gets the corresponding $f$-value according to the equation $\int \alpha \left(\nu \right)d\nu =\frac{\pi \mathrm{Nf}{e}^2}{m{c}^2}=(2.38\mathrm{}\times {10}^7)f$. The $f$-value calculated from this expression is 0.193 compared with 0.202 calculated from the dispersion measurements. The corresponding resonance wave-length from the dispersion measurements is 1468 in fairly good agreement with the observed position of the maximum of absorption. A dispersion formula which takes into account the distribution of absorption in a continuous band is given, and is applied to the dispersion of oxygen.