Just as it is nearly impossible to measure the length of a flea with a ruler containing 1cm gradations, observing phenomena occurring within an extremely short time span in the molecular world requires highly specialized tools. The ‘X-ray Scattering & Spectroscopy Lab’ led by professor Kim Kyung Hwan at the Department of Chemistry, POSTECH, harnesses the power of the PAL-XFEL which produces the ‘light of dream’ to ‘thoroughly’ probe into molecular structures and chemical reactions.

The cutting-edge PAL-XFEL generates light that is one billion times brighter than an x-ray. Such exceptionally brilliant light enables researchers to capture what happens on the femtosecond (one thousandth of a trillionth of a second) time scale in the microscopic world and to delve into those substances that exist for an extremely short time or perform exhaustive observations of the compounds being created.

With the help of the PAL-XFEL, the Lab observes inorganic catalysts, biologically-active proteins and other varying molecules to identify their properties which have been largely overlooked. One key example of this is the Lab’s research that pointed to the existence of a ‘Liquid-Liquid Critical Point (LLCP)’ through the molecular analyses of water which is different from general liquids. Scientists had long struggled to prove the hypothesis that water in its liquid form existed either as a high-density liquid or a low-density liquid, which is governed by such variables as temperature and pressure.  An LLCP is a critical point where these two types of local structures coexist at the exact ratio of unity, and water as we normally know it has already crossed its LLCP and thus exists with only one structure present.

Recently, the X-ray Scattering & Spectroscopy Lab produced highly noteworthy outcomes on the LLCP theory: its observations of ‘deeply supercooled water’ molecules, which exist in a liquid state even at subzero temperatures, eventually proved that water existed in two different phases at such low temperatures. Whereas supercooled water remains liquid for only a very short period of time, the PAL-XFEL allowed researchers to capture and analyze these fleeting moments.

As the PAL-XFEL is jointly used by scientists from all over the world, it gives the research team an opportunity to naturally mingle with world-renowned research groups and accumulate global experiences. The short-term goal of the X-ray Scattering & Spectroscopy Lab is to identify the exact locations of LLCPs, and the Lab aims to probe into the chemical reactions of numerous substances to help create materials that serve the pressing needs of humanity over the long haul. With the Lab aglow with a lively spirit, researchers are taking yet another step to explore the fundamental principles of matter.