The X-Ray Wavelength Scale in the Long-Wavelength Region

Abstract

AbstractRecently the X-ray wavelength scale has been put on a consistent basis by the selection of the W Kα1, line to be the wavelength standard foe the whole X-ray region of the electromagnetic spectrum. To help establish this scale, four other X-ray lines, which had been measured with a precision approaching 1 ppm, were selected as secondary standards. However, since the longest of these lines is the Cr Kα2 line at 2.293606 Å, other lines whose wavelengths are less precisely known have been used for calibration purposes. The most interesting of these is the Al Kα. line, which plays an important part in the effort to connect the X-ray wavelength scale to the basic standard of length. Two other often-used lines are the Cu La line at 13.339 Å and the O Kα line at 23.62 Å. It is, however, necessary to take several steps to trace the accepted values of these lines back to the basic X-ray wavelength standard. Furthermore, the uncertainties introduced by the effects of the chemical combination and the large natural line widths limit the precision obtainable. It has been suggested that the first resonance line of the Ne K edge in the 14-Å region would overcome both of these difficulties. It has also been suggested that the highfrequency limit of the bremsstrahlung radiation would make a particularly convenient reference mark. This method is discussed here, and it is shown that the accuracy obtainable by this method is better than that obtainable by means of some commonly used reference lines.