Experimental Evidence for the Filling of Electron Levels from the Relative Intensity of X-Ray Spectrum Lines

According to the accepted theory of the periodic system electrons first enter the $5_3$ orbits at 57 La; only one electron remaining in these orbits until 72 Hf from whence the orbits fill up to 10 electrons at 79 Au. The $L{\beta }_5$ line is double, representing the transitions $5_{32}$, $5_{33}$→$2_{22}$. In a previous paper the author found that this line was much more intense (about 37 times for $L{\beta }_5$ alone) in the uranium than in the tungsten $L$ series. This paper reports intensity measurements involving this line in 76 Os, 77 Ir, 78 Pt, 79 Au, 81 Tl, 82 Pb, 83 Bi. It is shown that experimental difficulties due to deposition of tungsten on the targets from the filaments may be avoided by keeping high vacua in the tubes. A curve showing the intensity ratio $\frac{{\beta }_5}{{\beta }_1}$ as a function of the atomic number rises with increasing atomic number and takes an upward jump between 78 Pt and 79 Au. This indicates that the first element in which 10 electrons occupy the $5_3$ orbits in an approximately undisturbed condition in the solid state is 79 Au. The curve is similar to one obtained in the region about 46 Pd for the lines $L{\gamma }_1$ and $L{\beta }_2$ by Jönsson.