X-ray Driven Trihydrogen Formation on Silica Nanosurfaces

2026/08/06 by Samuel Sahel-Schackis, Adam Summers, Ritika Dagar +29
Physics and Astronomy · #physics.chem-ph #astro-ph.GA #physics.atm-clus

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arxiv created 2026/08/06 · arxiv updated 2026/08/07

Abstract

The trihydrogen cation (H₃⁺) initiates the ion-molecule reactions that build molecular complexity in interstellar space. Whether its canonical formation reaction, H₂⁺ + H₂ → H₃⁺ + H, proceeds on inorganic surfaces under radiation-driven ionization has remained untested. Here we drive H₃⁺ formation on hydrated silica nanoparticles using intense 1.88 keV X-ray pulses, combining ion velocity map imaging, electron time-of-flight spectroscopy, and single-particle coherent diffractive imaging to resolve this chemistry on individual particles. The self-induced surface electric field on the V/nm scale drives interfacial charge transfer and water fragmentation. This field is the dominant parameter governing the relative yields of H⁺, H₂⁺, and H₃⁺ across particle size, composition, and aggregation. Density functional theory and nonadiabatic quantum molecular dynamics simulations trace this field-driven charge transfer, directly analogous to band bending at semiconductor photoelectrodes. These results establish surface-field-driven charge transfer as a unifying mechanism between radiation dominated astrophysical environments and field-driven surface catalysis.

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