The Absorption of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>K</mml:mi><mml:mi>α</mml:mi></mml:math>Line of Carbon in Various Gases and its Dependence upon Atomic Number

Abstract

A description is given of the apparatus and methods used in a photographic investigation of absorption coefficients for the $K\ensuremath{\alpha}$ line of the carbon ($\ensuremath{\lambda}=44.6\mathrm{A}$) in different gases and in gold leaf. The mass absorption coefficients, $\frac{\ensuremath{\mu}}{\ensuremath{\rho}}$, found were as follows: He, 3600: C${\mathrm{O}}_{2}$, 4780: ${\mathrm{N}}_{2}$, 3850: ${\mathrm{O}}_{2}$, 5765: Ne, 13100: A, 45700: Kr, 31800: Xe, 6740: Au, 12500. Some of the atomic absorption coefficients (${\ensuremath{\mu}}_{a}$) derived from these values on the assumption that the absorption is independent of chemical combination are as follows: C, 0.44\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}19}$: N, 0.89\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}19}$: O, 1.52\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}19}$: Ne, 4.36\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}19}$: The wave-length of the $K\ensuremath{\alpha}$ line of carbon lies between the $K$ and ${L}_{I}$ absorption limits of these elements. The values of $log{\ensuremath{\mu}}_{a}$ when plotted against $logZ$ fall upon a straight line whose slope is 4.4. Hence in this wave-length region this should be the value of $p$ in the equation ${\ensuremath{\tau}}_{a}=C{\ensuremath{\lambda}}^{n}{Z}^{p}$, provided that ${\ensuremath{\lambda}}_{K}&lt;\ensuremath{\lambda}&lt;{\ensuremath{\lambda}}_{L}$. The results of extrapolating current x-ray formulas to this wave-length are given and the values of ${\ensuremath{\mu}}_{a}$ so obtained are, in general, considerably too large. Since the exponent of $Z$ in the above equation is found experimentally to be as large or larger than in the case of ordinary x-rays it appears that the proper exponent of $\ensuremath{\lambda}$ may be considerably less than 3.