Microcanonical kinetics of water-mediated proton transfer in microhydrated 4-aminobenzoic acid

• 成果类型: Article
• 署名作者: Rana, Abhijit; Harville, Payten A.; Khuu, Thien; Johnson, Mark A.
• 署名单位: Yale University
• 刊物名称: SCIENCE
• ISSN/ISSBN: 0036-10097
• DOI: 10.1126/science.ady1723
• 发表日期: 2025-09-11
• 页码: 1143-1146
• 关键词: quadrupole ion-trap; photodissociation spectroscopy; aminobenzoic acid; gas-phase; resonance; ionization; transport

摘要

Isolated cluster systems can help to elucidate the molecular level description of water-mediated proton transfer. Protonation of neutral 4-aminobenzoic acid (4ABA) occurs at the acid (O-protomer) and amine (N-protomer) functionalities, yielding two distinct species with relative energies dependent on the degree of hydration. Here, we measured the rates of intramolecular proton transfer in 4ABAH+(H2O)6 ions upon protomer-selective vibrational excitation of initially cold (6 K) cluster ions isolated in a cryogenic ion trap. Interconversion rates were observed on the microsecond time scale. These results quantify the kinetics of proton transfers in the context of a closed, finite system at well-defined internal energies and therefore provide experimental benchmarks for theoretical efforts that are being developed to treat relatively slow, highly cooperative solvent-mediated chemical processes.