Pressure-Induced Reverse Reaction of the Photochemical Decomposition of Germanium Tetraiodide Molecular Crystal

Abstract

GeI₄ molecular crystal and its solution in cyclohexane were irradiated by lasers of different wavelengths to investigate the critical wavelength for photochemical decomposition of GeI₄. We have observed that 633 nm laser can photochemically decompose GeI₄, exceeding the previously reported wavelength limit of 514 nm. XPS spectra indicate that GeI₄ is photochemically decomposed into Ge₂I₆ and I₂; unlike GeBr₄, Ge²⁺ (GeI₂) cannot be found in the photochemical reaction products. Raman spectra measurement of GeI₄ under high pressure up to 24 GPa show that Raman signals of Ge₂I₆ and I₂ vanish at 0.5 to 1.7 GPa. This finding clearly shows that high pressure can effectively reverse the photochemical decomposition of GeI₄ and influence the direction of the solid-state reaction, which is usually found on gas-phase reactions