A New Approach for Investigation of High-resolution Ion-neutral Collisions

With support from the Chemical Structure and Dynamics (CSD) program in the Division of Chemistry, Professor Zhou of the University of Nevada, Las Vegas is developing a state-of-the-art experimental platform for ion-neutral collision studies, focusing on molecules prevalent in the interstellar medium (ISM). This platform aims to replicate ISM conditions in a laboratory setting, covering a broad temperature range (10-5000 K) while ensuring high resolution, sensitivity, and minimal background. Accurately reproducing astrochemical reactions in the lab requires precise control over reactants, a challenge that is particularly complex for molecules containing carbon (C), hydrogen (H), oxygen (O), and nitrogen (N). To overcome this challenge, Professor Zhou and his students will demonstrate precise manipulation and broad tunability of collision energy using a merged beam configuration, where the neutral beam originates from a cryogenic buffer gas cell, and the ion beam is generated within a ring-shaped ion trap. Their work could lead to the establishment of a forefront astrochemistry facility, advancing our understanding of the molecular mechanisms shaping the universe. As the first experimental platform at the Nevada Center for Astrophysics (NCfA), it will expand NCfA’s mission into laboratory astrophysics, drive cutting-edge research, enhance STEM education, and attract top talent, further elevating the institution’s research profile. The proposed method centers on the ability to transport ions at the same velocity as neutral species, enabling low-energy collisions in a moving frame. Unlike pulsed beam experiments, this approach utilizes a ring-shaped RF trap to confine the ion beam, making it conceptually closer to static hybrid trap setups, where ion traps overlap with magneto-optical traps. In this configuration, the axial secular frequency of the trapping potential is significantly higher than the circular frequency of ion motion. This key feature distinguishes it from high-energy ion beams in storage rings. As a result, this method offers precise control over ion velocities, ranging from stationary to several thousand meters per second, enabling the study of collisions across a wide energy spectrum with high resolution. The system’s fine control over ion velocity makes it particularly well-suited for interfacing with supersonic or buffer gas-cooled molecular beams, allowing for precise manipulation of collision dynamics. Furthermore, the proposed approach enables extended interrogation periods lasting over a second. This prolonged interaction time is critical for studying slow ion-neutral reactions, allowing for the observation of detailed reaction dynamics that would otherwise be missed in shorter timescales. Enhanced duration not only provides greater control and precision but also significantly improves resolution in analyzing reaction mechanisms. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.