Ion’s hidden transformation process has been revealed. The research team led by Hyocheol Lee (Professor of Chemistry, KAIST) of the Advanced Reaction Dynamics Research Center at the Institute for Basic Science (IBS) observed the process of the creation and change of gaseous ions in real time. In this process, we found that ions form products through previously unknown stages, such as a structural dark state.
From real life to space, ions play an important role everywhere. From the lithium-ion batteries in smartphones to the energy we eat when absorbed, the light and energy coming from the sun, etc. are all the result of ionic activity.
However, despite its importance, not much research has been done on changes in the structure and shape of ions. This is because it is difficult to experimentally observe changes in time and space of ions that move minutely at the level of several angstroms (one billionth of a centimeter) in a split second of a few picoseconds (one trillionth of a second). In particular, it has been more difficult to observe the dynamics of gas-phase ions isolated from the surrounding system.
In previous research, researchers have identified the moment when a molecular bond is broken (Science, 2005), the moment a molecule is born through a chemical bond (Nature, 2015), and the molecular structure of the entire process from the beginning to the end of a chemical reaction (Nature, 2020). It has been observed at this level. At the time, the research was conducted using X-rays, but an experiment with higher sensitivity was needed to observe the dynamics of ions.
Accordingly, the researchers used ‘Megaelectronvolt ultrafast electron diffraction (MeV-UED)’ equipment, which was designed to see faster and smaller movements. Here, the ‘resonance-enhanced multiphoton ionization technique’ was applied to generate specific ions in large quantities to the point where they could be observed in experiments.
Schematic diagram of a megaelectronvolt ultrafast electron diffraction experiment for dibromopropane molecules. Source: IBS
In this process, we also captured the unique behavior of ions that are different from molecules in a neutral state. In this study, we observed the process of generation and structural change of cations derived from 1,3-dibromopropane (DBP, C3H6Br2), and observed ‘structural dark states’ in which no structural changes occur after cations are generated. The phenomenon of retention was discovered for the first time. The state of structural darkness is said to have lasted for about 3.6 picoseconds. After about 15 picoseconds, the DBP cation was converted to an intermediate containing a loosely bound bromine (Br) atom, and after 77 picoseconds, the bromine atom was separated and finally formed a bromonium ion ((C3H7Br)+).
“This study is significant as the first to track the structural dynamics of molecular ions in real time,” said first author Heo Jun, an invited research fellow. “As it has expanded our understanding of gas ions, it has expanded our understanding of chemical reaction mechanisms and changes in material properties. “It is expected to provide new insights in various fields such as space chemistry and space chemistry.” Student researcher Kim Do-young, the first author, said, “Ions are highly reactive and do not exist for a long time, and it is difficult to selectively synthesize only one type, making it difficult to observe structural changes in real time.” He added, “The generated gas ions do not directly indicate structural changes. “We found that it maintains a certain shape and then shows drastic changes,” he explained.
Director Lee Hyo-cheol, who led the research, said, “This research has uncovered the hidden secrets of ions, which are common but have not been revealed. Although science and technology have made remarkable progress, there are still amazing secrets of the material world that we do not know and that scientists must unravel.” “There are a lot of them,” he said.
The research results were published in the online edition of the international academic journal ‘Nature’ on January 11th at 01:00 (Korean time).
논문명: Capturing the generation and structural transformations of molecular ions
Copyright © My Neighbor Scientist Unauthorized reproduction and redistribution prohibited
