“Intense Reactivity in Sulfur−Hydrogen Mixtures at High Pressure under X‑ray Irradiation”
E.J. Pace, A.L. Coleman, R.J. Husband, H. Hwang, J. Choi, T. Kim, G. Hwang, S.H Chun, D. Nam, S. Kim, O.B. Ball, H.-P. Liermann, M.I. McMahon, Y. Lee, and R.S. McWilliams
Journal of Physical Chemistry Letters
Vol.11, pp.1828-1834, 2020.02
Superconductivity near room temperature in the sulfur–hydrogen system arises from a sequence of reactions at high pressures, with X-ray diffraction experiments playing a central role in understanding these chemical–structural transformations and the corresponding S:H stoichiometry. Here we document X-ray irradiation acting as both a probe and as a driver of chemical reaction in this dense hydride system. We observe a reaction between molecular hydrogen (H2) and elemental sulfur (S8) under high pressure, induced directly by X-ray illumination, at photon energies of 12 keV using a free electron laser. The rapid synthesis of hydrogen sulfide (H2S) at 0.3 GPa was confirmed by optical observations, spectroscopic measurements, and microstructural changes detected by X-ray diffraction. These results document X-ray induced chemical synthesis of superconductor-forming dense hydrides, revealing an alternative production strategy and confirming the disruptive nature of X-ray exposure in studies on high-pressure hydrogen chalcogenides, from water to high-temperature superconductors.