The Position and Structure of the Modified Line of the Spectrum of Scattered X-Rays

Measurements have been made by both photographic and single-crystal ionization methods of the shift in wave-length of scattered x-rays at angle of about 170^∘{}. The photographic method was that introduced by Sharp, but the Kβ line of molybdenum was used. Two exposures of several hundred hours each were obtained. Analyses of the microphotographic records gave, from the shift of the center of gravity of the lines, h/mc=0.02305A, and from the shift of the peaks, h/mc=0.2374A. From the difference between different exposures, it is suspected that some hidden source of error is present, perhaps due to the effect of the Kγ line. Some 600 ionization curves give as an average h/cm=0.0240±0.00024A. These results, compared with those of other experimenters, fail to indicate any definite departure from the theoretical value of h/mc=0.2422A. This does not support the findings of Davis and Purks, who report a value of 0.022A. The form of the spectral lines observed seems inconsistent with a fine structure of the modified line such as reported by Davis and Purks. The modified line is however found to have a considerable natural breadth.