Rayleigh scattering from crystals and amorphous structures

A cryogenic chamber for scattering measurements

“…The thermal behavior of the chamber was tested with the cell ®lled with liquid xenon, which can exist in the liquid phase between À112°C and +16°C (triple and critical points, respectively), the pressure of gas in contact with the liquid varying between 0.8 and 58 bar, respectively. Within this range of temperatures the liquid density varies between 3.1 and 1.1 g/cm 3 . In order to achieve the required low temperature, a bath of ethyl alcohol cooled with liquid nitrogen was used whose temperature is monitored by a thermoresistor.…”

“…1) connecting the extremities of the cell. The temperature is monitored by two platinum thermoresistors 3 glued on the top and the bottom of the inner cell. The entrance of gas, as well as the evacuation of the inner cell, is made through a long stainless steel tube (B 3 mm) wound in a helical form and connected by a Swagelok 4 coupling to the top¯ange of the outer vessel.…”

“…1. It includes an aluminum inner cell (B 20´50 mm 3 inner dimensions, 1 mm wall thickness), where the liquid sample is condensed, which was dimensioned in view of the tests with liquid xenon and 662 keV c-rays. Hence, its inner diameter is smaller than the mean free path of those photons in that medium (%4 cm).…”

“…In the case of photon scattering involving small momentum transfer (typically corresponding to x < 2 # A À1 ) in complex environments like crystals, polycrystalline aggregates and liquids, the structure of the medium leads to interference eects [3]. For liquids, few experimental and theoretical data are available [3±5].…”

“…In many cases the scattering process can still be described as being due to free atoms, depending on factors like temperature, atomic number or preparation of the sample. Hence, each particular case has to be investigated before using the free atom approximation [3]. Such complex structures are specially important in appliances involving X-and c-rays.…”