Fluorine Chemistry at Extreme Conditions: Possible Synthesis of Hgf4

By irradiating a pressurized mixture of a fluorine-bearing compound (XeF2XeF2) and HgF2HgF2 with synchrotron hard x-rays ... (See full text for complete abstract

The High Pressure Dependence of X-Ray Induced Decomposition of Cadmium Oxalate

The high proclivity of x rays to destabilize and distort molecular structures has been previously utilized in the synthesis of novel compounds. Here, we show that x-ray induced decomposition of cadmium oxalate induces chemical and structural transformations only at 0.5 and 1 GPa. Using x-ray diffraction and Raman spectroscopy, the synthesized product is identified as cadmium carbonate with cadmium oxalate remnants, which is stable under ambient conditions. At ambient and \u3e1 GPa pressures, only degradation of the electronic density distribution is observed. The transformation kinetics are examined in terms of Avrami’s model, which demonstrates that despite the necessity of high pressure for efficient x-ray induced synthesis of cadmium carbonate, the rate and geometry of structural synthesis in the 0.5–1 GPa pressure range do not depend on the applied pressure. In addition, the possible role of intermolecular distance and molecular mobility in transformation yield is also discussed. Our experimental results indicate that x-ray induced photochemical synthetic pathways can be modulated and optimized by specific parameter selection such as high pressure

Measurement of the Energy and High-Pressure Dependence of X‑ray-Induced Decomposition of Crystalline Strontium Oxalate

We report measurements of the X-ray-induced decomposition of crystalline strontium oxalate (SrC₂O₄) as a function of energy and high pressure in two separate experiments. SrC₂O₄ at ambient conditions was irradiated with monochromatic synchrotron X-rays ranging in energy from 15 to 28 keV. A broad resonance of the decomposition yield was observed with a clear maximum when irradiating with ∼20 keV X-rays and ambient pressure. Little or no decomposition was observed at 15 keV, which is below the Sr K-shell energy of 16.12 keV, suggesting that excitation of core electrons may play an important role in the destabilization of the C₂O₄^2– anion. A second experiment was performed to investigate the high-pressure dependence of the X-ray-induced decomposition of strontium oxalate at fixed energy. SrC₂O₄ was compressed in a diamond anvil cell (DAC) in the pressure range from 0 to 7.6 GPa with 1 GPa increments and irradiated in situ with 20 keV X-rays. A marked pressure dependence of the decomposition yield of SrC₂O₄ was observed with a decomposition yield maximum at around 1 GPa, suggesting that different crystal structures of the material play an important role in the decomposition process. This may be due in part to a phase transition observed near this pressure