A Precision Study of the TungstenKSpectrum Using the 2-Meter Focusing Curved Crystal Spectrometer

Using the 2-meter focusing curved crystal gamma-ray spectrometer, careful measurements were made of the wave-lengths of the $K$ series lines and $K$ absorption edge of tungsten for the dual purpose of establishing a precision linkage between wave-length measurements in the gamma- and x-ray regions and of improving our knowledge of the tungsten wave-lengths. The high precision, resolution, and luminosity of the instrument made possible the complete resolution of the $\beta$-doublet, the partial resolution of the $\gamma$-doublet, and the detection and measurement of a $\delta$-line close to the absorption edge. Absolute determinations of the Bragg angles for Mo $K{\alpha }_1$ and W $K{\alpha }_1$ reflected from the (310) planes of quartz by W. J. West in this laboratory, using a precision 2-crystal spectrometer, are described. These were undertaken (a) to standardize the tungsten $K$ spectrum with higher accuracy in terms of the Siegbahn scale of x-ray wave-lengths and (b) to yield on this scale a precision determination of the grating constant of the quartz (310) planes. Adopting W. J. West's value of 208.575±0.008 x.u. (Siegbahn scale) for the wave-length of the ${\alpha }_1$ line, the wave-lengths of the $K$ series lines and $K$ edge were found to be: