The Natural Widths of theK-Series of W(74)

By means of a two-crystal x-ray spectrometer of high resolving power at short wave-length, the full widths at half maximum of the $K$-series of W(74) have been measured. The observed widths $W_O$ in the (1,+1) position of the crystals have been corrected to true widths $W_T$ by use of the formula $W_T=W_O-W_R$ where $W_R$ is the width of the rocking curve of the crystals in the (1,-1) position. It is shown that, in the short wave-length region under consideration the (1,-1) rocking curves obey the Hoyt equation. By using Weisskopf's equation for the shape of a spectral line, the above correction formula results. The following (corrected) full widths at half maximum (in volts) are obtained: $K{\alpha }_2$, 43.3; ${\alpha }_1$, 43.0; ${\beta }_3$, 50.0; ${\beta }_1$, 48.6; ${\gamma }_2$, 37.0; ${\gamma }_1$, 37.0; ${\delta }_2$, 34.0; ${\delta }_1$, 34.