X선 회절 및 분광학 연구실

X-ray science has evolved dramatically in the 21st century with the use of large X-ray facilities. Recently developed X-ray free electron lasers (XFELs) such as LCLS, SACLA, PAL-XFEL, European XFEL, can generate ultrashort X-ray pulses with unprecedented brilliance and coherence that is a billion times higher than that of the best conventional X-ray radiation sources. This has been a breakthrough for many X-ray related techniques on a broad range of scientific disciplines and brought us to investigate many interesting new sciences which was previously not possible. Our group utilize X-ray scattering, X-ray spectroscopy, and X-ray photon correlation spectroscopy to study the structural origin of water (ice) anomalies, catalytic reactions, and protein dynamics. Water is the most important liquid for our existence and plays an essential role in physics, chemistry, biology and geoscience. Water has numerous physical and chemical properties which are very different from other liquids, which are often referred to as anomalous. As an explanation for these anomalous experimental observations, a hypothetical liquid-liquid transition (LLT) and a liquid-liquid critical point (LLCP) has been proposed deep in the supercooled regime, but never been experimentally observed. Recently, with a new method of rapid cooling down to 227 K and ultrafast probing with static WAXS, the first experimental evidence of the existence of the Widom line which strongly indicates the existence of LLCP has been reported. With an external perturbation, we aim to have a direct search of the LLCP using SAXS and WAXS. And we also aim to reveal the existence of fragile-to-strong transition of liquid water. Another major challenge in understanding solution-phase chemistry arises from the presence of numerous s