ANOMALOUS BOND-LENGTH EXPANSION IN LIQUID IODINE AT HIGH-PRESSURE

We have performed an x-ray absorption spectroscopy experiment on iodin e under extreme conditions up to 6 GPa and 1050 K, using a large volum e pressure cell. We measured the bond length of It in the room-tempera ture solid phase and in the liquid phase just above the melting curve, as a function of pressure. Our results show that for the solid it is nearly constant, while in the liquid it strongly increases and at 2.1 GPa becomes larger than in the solid. Indication of molecular dissocia tion in the liquid phase at approximate to 1000 K and 4.5 GPa is obtai ned.