No abstract

The absolute intensity of small-angle x-ray scattering has been measured by two methods—comparison with a beam transmitted through a series of similar attenuators, extrapolated to the case of no attenuators, and comparison with the scattering of air—with good agreement. Some reproducible substances are calibrated as standards at small angles and some also at larger angles, in the range accessible to the diffractometer. Brief interpretations are given of the small-angle scattering; that of water is consistent with theory. The long-range density fluctuations of vitreous silica are found to be mainly those frozen in at the glass transformation. The absolute scatterings are compared with Katz's unpublished small-angle standardization and with Warren's standardizations of Lucite and vitreous silica by means of high-angle scattering. Katz's measurements of silica and Warren's of Lucite are appropriate for quantitative comparison. They are about 2% higher and 7% lower, respectively, than the present result. Finally, the effect of impurities is derived.

No abstract

The properties of second-harmonic light scattering in fluids are derived in terms of the molecular polarizabilities, orientation correlation among molecules, and the molecular field Fα. Measurements of scattering intensity in CCl4 and water, from about 10° to 60°C, are reported. The variations with temperature, and therefore apparently the effects of changes of orientation correlation, are slight. The influence of preferred orientation in CCl4, of the type deduced from x-ray diffraction, is calculated. The third-rank molecular polarizability tensor consists of a fourth-rank tensor contracted with Fα, in addition to the term previously known, which is independent of Fα. With Fα arising from molecular multipole moments, the new term explains some measured depolarizations in liquids, and accounts for the spectral line, but not the background, observed in methane gas. In the case of molecular dipole moments, the new term can cause spectral narrowing.