Fine Structure in the K -Series of Copper and Nickel and the Width of Spectral Lines

Width and fine structure of the Kα₁, Kα₂ and Kβ lines of Ni, Cu, Mo and Ag.---High resolving power was obtained by means of the double x-ray spectrometer. The minimum width of slits was 1.75 mm. Wide slits made possible the study of the lines after second order reflection from two calcite crystals. Ionization currents were measured with a Compton type electrometer of sensitivity 5000 mm per volt at one meter. At 40 kv and in the first order the widths at half-maximum of the lines (in X.U.) were found to be: Ni Kα1,2, 0.66; Cu Kα1,2, 0.63; Mo Kα1,2, 0.47; Ag Kα1,2, 0.43; Mo Kβ1,2, 0.43; Ag Kβ1,2, 0.40. In the second order the estimated width of the components of Ni Kα1,2 and Cu Kα1,2 was 0.4 X.U. which was also the estimated width of Ni Kβ1,2 and of Cu Kβ1,2. Structure to the lines of nickel and copper was clearly indicated by the shapes of the curves. The first order curves of the Kα lines of Ni and Cu showed an asymmetry on the long wave-length side which was checked as regards position and intensity by the second order curves. It was found that the lack of symmetry could be explained by the presence of weak lines at displacements 0.42 and 0.35 X.U. from Cu Kα₁ and Cu Kα₂, respectively, and 0.45 and 0.38 X.U. from Ni Kα₁ and Ni Kα₂, respectively. The Kβ doublets of Mo and Ag were clearly resolved after first order reflection from two crystals. Their separations were, for Ag Kβ₂-Kβ₁ 0.63 X.U. and for Mo Kβ₂-Kβ₁, 0.58 X.U. These doublets for Ni and Cu were not resolved after second order reflection. However, the shapes of the curves obtained permitted a solution of the problem of intensities and displacements. Their separations were 0.32 X.U. and 0.29 X.U. for Cu Kβ₂-Kβ₁ and Ni Kβ₂-Kβ₁, respectively. The shapes of the Kβ curves of Ni and Cu showed evidence of the spark line Kβ^' and the curve of Cu showed evidence of a line corresponding to the Kβ^'' line found by Hjalmer for Ca, K, Cl.Variation with potential of the width of the Kα lines of Ni, Cu, Mo and Ag.---Curves showing a variation of width of the Kα lines with voltage were obtained. The widths increased with increasing voltage but seemed to approach a limiting value at about 40 kv. The width at the excitation potential was about two-thirds the width at 40 kv. The variation is explained as due to the successive appearance of spark lines.