8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Fri 911:10-14:00P1.23X-ray Compton scattering measurements of expandedfluid rubidiumKazuhiro Matsuda, 1 Takena Nagao, 1 Yukio Kajihara, 2 Koji Kimura, 3 MasanoriInui, 2 Kozaburo Tamura, 4 Makoto Yao, 3 Masayoshi Itou, 5 and Yoshiharu Sakurai 51 Department of Physics, Graduate School of Science, Kyoto University,Kitashirakawaoiwake-cho, Sakyo-ku, 606-8502, Kyoto, Japan2 Graduate School of Integrated Arts and Sciences, Hiroshima University, HigashiHiroshima, Japan3 Department of Physics, Graduate School of Science, Kyoto University, Kyoto,Japan4 Graduate School of Engineering, Kyoto University, Kyoto, Japan5 Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo, JapanLiquid metals near the triple point exhibit typical metallic characters, whereas a vapor is insulating.The formation of an insulating vapor from metallic liquid has been posing a fundamentalproblem in condensed matter physics and its elucidation requires the essential understandingof electron-ion and electron-electron correlation effects. Fluid metals are an ideal system toinvestigate the variation in the interparticle interaction accompanying a metal-insulator transitionbecause a systematic reduction in density is possible by controlling temperature and pressurewithout crossing the liquid-vapor saturation curve. We have thus far carried out x-ray diffractionmeasurements for expanded fluid rubidium up to the supercritical regions and found that theinteratomic distance contracts in spite of the fact that the average interatomic distance increaseswith volume expansion. The results suggest that the attractive force among ions is enhancedwith decreasing density and the charge fluctuations of the low-density interacting electron gasplay an essential role for that enhanced attractive force [1]. Synchrotron-based x-ray Comptonscattering has been a well-established technique for measuring the electron momentum density inmaterials and also provides an opportunity to perform the experiments on the electronic state athigh temperatures and pressures. We have developed a specially designed vessel and succeededto measure Compton profiles of fluid rubidium from near the melting point up to supercriticalregions (2123 K and 13.0 MPa). It was found that difference between the experimentally obtainedCompton profiles and those estimated by the free electron gas model was pronounced with decreasingfluid density, indicating the electronic state markedly deviates from that of the free electron gas.[1] K. Matsuda, K. Tamura, M. Inui, Physical Review Letters, 98, 096401 (2007).23