Widths of theLx-ray lines of the rare-earth elements

An improved version of a single-crystal high-angle goniometer and a NaI scintillation detector were used to measure the widths of the $L {\alpha }_{1.2}$, $L {\beta }_{1-4}$, and $L {\gamma }_1$ x-ray lines of the elements $58\le Z\le 74$ and the widths of the less prominent lines $L {\beta }_{15}$, $\mathrm{Ll}$, $L\eta$, and $L{\gamma }_1^{\prime }$ of several elements in the same group. The x-ray spectrum of these elements was produced by bombarding them with an electron beam of constant energy and flux, and a computer program was used to unfold the physical widths of their emission lines. These results, as well as the previously reported values of linewidths of the higher-$Z$ elements, are compared with the most recent theoretical predictions.