Observation of electron-transfer-mediated decay in aqueous solution

Area of Science:

• Physical Chemistry
• Surface Science
• Spectroscopy

Background:

• Photoionization is fundamental to X-ray photoelectron spectroscopy (XPS), providing insights into chemical environments.
• Electronic decay processes following photoionization, including local and non-local decay, are well-understood.
• Electron-transfer-mediated decay (ETMD) in condensed phases remained experimentally unconfirmed until this study.

Purpose of the Study:

• To experimentally observe and characterize electron-transfer-mediated decay (ETMD) in a condensed phase system.
• To investigate the role of solvent molecules and counterions in ETMD processes within an aqueous solution.
• To establish spectral fingerprints for different ion associations and their sensitivity to structural parameters.

Main Methods:

• Utilizing liquid-microjet soft X-ray photoelectron spectroscopy (XPS) to probe an aqueous LiCl solution.
• Employing molecular dynamics simulations to interpret experimental observations.
• Performing high-level ab initio calculations to elucidate ETMD mechanisms.

Main Results:

• The first experimental observation of electron-transfer-mediated decay (ETMD) in an aqueous LiCl solution.
• Detection of characteristic secondary low-energy electrons associated with ETMD.
• Identification of distinct spectral signatures for various ion-solvent and ion-ion associations.
• Demonstration that ETMD spectra are sensitive to coordination numbers, ion-solvent distances, and solvent arrangements.

Conclusions:

• Electron-transfer-mediated decay (ETMD) is a viable electronic decay pathway in condensed phase ionic solutions.
• Solvent molecules and counterions actively participate in ETMD, influencing spectral characteristics.
• ETMD spectroscopy offers a sensitive probe for the local structure and dynamics of ions in solution.