X-ray diffraction studies of fluid rubidium: From the liquid to a dense vapor

Abstract X-ray diffraction measurements have been carried out for fluid rubidium from the triple point up to supercritical conditions using synchrotron radiation at SPring-8. In order to achieve high- temperature diffraction experiments, we have developed a new sample cell made of molybdenum that is resistant to the highly corrosive nature of hot alkali metals. The use of the cell has made it possible to achieve stable and precise measurements at the supercritical region of fluid rubidium. It was observed that the position at the first peak of the pair distribution function starts to decrease around 1.0 g/cm3 with decreasing density, suggesting the possibility of dimerization in the density range where the fluid is still metallic.