EAGER: Vibrational Electron Energy Loss Spectroscopy - A New Nanometer Probe for Planetary Materials and Volatiles

Arizona State University, Scottsdale AZ

Investigators

Abstract

Water is crucial for life on Earth, and understanding how it cycles and is stored within the Earth is key to understanding its habitability. The Earth's interior is one of the least understood areas in this regard. Some minerals in the Earth's deep layers can hold water within their atomic structures. Although these minerals contain only a small amount of water, the vast size of the Earth's interior means it could potentially hold much more water than all of the oceans on the surface combined. However, detecting and measuring this water is difficult because the water is present in such small quantities and the samples from deep within the Earth or synthesized in labs are very small. Researchers at Arizona State University are developing new methods using a technique called vibrational electron energy loss spectroscopy (vibEELS) with advanced electron microscopes to measure water in these minerals down to the nanometer scale. This will also allow them to analyze the structure of minerals in detail, a task that was very challenging with existing methods. They are working on techniques to measure both the amount of water and the structure and chemical composition of these water-containing minerals simultaneously. This research will set up new analytical methods at Arizona State University and Brookhaven National Laboratory for use by Earth scientists widely. Researchers will also develop and share open-source software for analyzing these measurements. The research team will host a workshop to share these new techniques to a wider group of Earth and environmental scientists. The project will also provide research opportunities for undergraduate and graduate students at Arizona State University. The project aims to establish protocols for vibrational electron energy loss spectroscopy (vibEELS) using the Nion ultra-STEM. The primary objectives are to: (1) quantify H2O in minerals and quenched melts at the nanometer scale; (2) conduct structural analyses of minerals through single-crystal vibrational spectroscopy; and (3) integrate vibEELS with electron diffraction, energy-dispersive spectrometry, electron energy loss spectroscopy, and imaging for comprehensive mineral analyses. Despite hydrogen loss during Earth's formation, significant amounts remain in the interior, likely equivalent to multiple oceans. This hydrogen is crucial in the geological water cycle, influencing magma and rock properties. Accurate methods are needed to study hydrogen’s atomic-scale integration and quantify its storage in minerals and melts. Existing techniques like SIMS, NanoSIMS, Raman, and infrared spectroscopy have limitations in spatial resolution and structural information. The Nion ultra-STEM, with its energy resolution, enables vibEELS to measure electron energy loss from lattice vibrations with excellent nanometer spatial resolution, suitable for multi-phase samples which is common for Earth science research. Preliminary vibEELS measurements on hydrous ringwoodite, hydrated CaTiO3 perovskite, and stishovite have shown promising results. VibEELS can detect both OH and H2 bands. Integrating vibEELS with electron diffraction allows for noble analyses of vibrational mode intensity and crystallographic orientation. This project aims to harness vibEELS to offer new insights into hydrogen’s role in Earth’s interior. The work plan is designed to maximize the research's broader impact by: (1) establishing vibEELS workflows at ASU’s Eyring Materials Center and Brookhaven National Laboratory; (2) developing open-source software for vibEELS analysis; and (3) hosting a vibEELS workshop at the Fall American Geophysical Union meeting in the second year. By introducing innovative analytical techniques and providing open access to these tools, the project aims to benefit the Earth science community significantly. 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.