X-ray Absorption Coefficients of Mercury Vapor in the Region of itsL-Absorption Discontinuities

An apparatus is described which is suitable for absorption measurements up to 2 or more angstroms. The absorber, which was in the form of superheated vapor whose density could be calculated on the assumption of perfect gas behavior, was contained in an all-glass chamber. The windows were constructed of thin glass films in such a way as to withstand atmospheric pressure from either side. The mass absorption coefficients, $\frac{\mu }{\rho }$, of mercury in the wave-length region 0.74 to 1.4A were determined by an ionization method. They were found to obey the relation $\frac{\mu }{\rho }=A{\lambda }^c$, where the constants $A$ and $c$ vary from branch to branch of the $\frac{\mu }{\rho }$, $\lambda$ curve. The value of $c$ is 2.56 on the short and 2.66 on the long wave-length side of the $L$ discontinuities. The magnitudes, $\delta$, of the three $L$ absorption discontinuities, where $\delta$ is defined as the ratio of $\frac{\mu }{\rho }$ (the scattering coefficient being neglected) on the short and long wave-length sides of an absorption limit, are $\delta L_{\mathrm{I}}=1.18\mathrm{} \delta L_{\mathrm{II}}=1.39\mathrm{} \delta L_{\mathrm{III}}=2.45\mathrm{}$