Establishing x-ray-induced non-local decay as a probe to the first solvation shell

• Grant number: 24/17762-5
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date until: January 01, 2025
• End date until: December 31, 2027
• Field of knowledge: Physical Sciences and Mathematics - Physics - Atomic and Molecular Physics
• Principal Investigator: Arnaldo Naves de Brito
• Grantee: Alan Guilherme Falkowski
• Host Institution: Instituto de Física Gleb Wataghin (IFGW). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Weakly bonded systems play an essential role across multiple scientific fields, including biology, chemistry, sensor technology, and cancer therapy. A common theme in these areas is the critical role of the liquid interface at the molecular level. Among liquids, water stands out due to its vital connection to life and its unique hydrogen-bonding properties. These properties differ between bulk water and the water in the first solvation shell (FSS), which is known to significantly influence protein folding, charge transfer, and chemical reactivity. Despite its fundamental role, probing the geometrical and electronic properties of the water FSS has been challenging, limited to advanced techniques like neutron diffraction, NMR, and X-ray scattering. Even fewer studies have focused on the electronic structure and dynamics of the FSS due to the limitations of current probing methods.Recently, new spectroscopic techniques using X-rays have emerged, with the potential to provide detailed insights into the geometrical and electronic properties of the FSS. If the surrounding water electrons fill a core hole, a process known as non-local decay (NLD) occurs. Studies have shown that NLD provides a precise spectroscopic signature, revealing the electronic characteristics of the FSS in unprecedented detail. This project aims to explore this novel technique both theoretically and experimentally.One promising application of this new X-ray technology lies in the field of sensors. Sensors are crucial in fire detection, disease diagnosis, optoelectronics, human-machine interfaces, and even elementary particle detection. Biosensors, in particular, have been the focus of recent research, including their role in diagnosing diseases like dengue fever transmitted by the Aedes Aegypti mosquito. In many of these applications, the charge transfer behavior at a microscopic level is critical, particularly in aqueous environments where many sensors operate.To investigate non-local decays in these contexts, this project proposes a stepwise approach, beginning with simple systems and progressing to more complex ones. The initial focus will be on studying the first water solvation shell around metal ions (e.g., Li¿, Na¿, Mg²¿, Al³¿) using resonant inelastic X-ray scattering (RIXS) and X-ray emission spectroscopy (XES). By examining the influence of the FSS on charge transfer dynamics and the probability of non-local decay processes, this research seeks to deepen our understanding of charge transfer in aqueous environments, paving the way for advancements in sensor technology and other fields reliant on weakly bonded systems.