The Effect of Temperature on the Scattering of X-rays by Crystals

Variation of the Scattering of X-Rays by Rocksalt and Calcite with Temperature.---Using x-rays from the W target of a Coolidge tube operated at 95 kv., the ratio of the radiation scattered from a crystal at 295^∘{}C. to that scattered at the same angle from the crystal at 17^∘{} C. was found to be: 1.33 and 1.18 ±{}.10 for rocksalt and angles of 15^∘{} and 30^∘{} respectively, and 0.99 and 1.03 ±{}.04 for calcite and angles of 30^∘{} and 73^∘{} respectively. Thus there is a marked effect for rocksalt but apparently none for calcite, which seems to scatter x-rays like an amorphous substance. Comparison with the Debye theory shows that even for rocksalt the effect is considerably smaller than that theoretically predicted, whether zero-point energy is assumed or not, while for calcite the disagreement is marked.