Density effect on molecular bond length in fluid I2 by x-ray absorption spectroscopy

Precise measurements of x-ray absorption spectra above the I K-edge both in the low-density gas in a wide temperature range and in the liquid along the coexistence curve have been performed. By using an advanced data analysis procedure it was possible, for the first time, to reveal changes in the structure of the I2 molecule in the liquid as a function of density. The relevance of these changes and the possible correlations with other peculiar properties of liquid I2, and in particular with the metallization transition observed in the liquid under pressure, are discussed.