The study of collisions between cold molecules has attracted much attention in recent years. This research could enable us to understand the most fundamental aspects of molecular interactions and the progress of this research makes it possible to achieve the goal of manipulation and control of chemical reactions. Furthermore, the full understanding of cold molecular collisions could shed new light on some important puzzles in the Earth’s atmospheric and interstellar chemistry. However, to date, the study of cold molecular collisions remains largely unexplored, due to a huge challenge in the experimental approach. For instance, techniques for obtaining high-quality molecular beams and high-resolution state-to-state resolved detection for the crossed molecular beam experiment are rarely available.
In this project, we used a new crossed-beam scattering experimental method combined with a multistage Zeeman decelerator and recoil-free resonance-enhanced multiphoton ionization (REMPI) detection schemes, which allowed us to investigate the dynamics of cold and controlled molecular collisions with unprecedented resolution in a new, previously inaccessible, regime.
We successfully combined Zeeman deceleration and Vacuum-Ultraviolet detection (VUV) based recoil-free REMPI detection and upgraded our setup to reach previously inaccessible collision energies by reducing the crossed beam angle to only 4 degrees. Using this experimental approach, we investigated scattering resonance effects for C + He, H2 inelastic collisions. We measured angular scattering distributions of the scattered C atoms and found that the differential cross section (DCS) changes rapidly as a function of collision energy when the C atoms collided with H2 molecules. These measurements provided a very sensitive test for the potential energy surfaces that describe the interactions between the colliding particles. Afterwards, we successfully investigated the reactive collision between electronically excited sulfur atoms and hydrogen molecules. We for the first time measured quantum-state-resolved scattering images of the reaction products for this reaction.
Our results have provided and will provide a critical test for current models of chemical processes taking place in the Earth's atmosphere and in interstellar space. In the future, we hope to be able to manipulate and control chemical reactions based on the knowledge gained during this project.
