Towards the metallization transition in liquid I2:: A spectroscopic study

Optical absorption spectra of liquid It at different densities and temperatures were measured using an externally heated diamond anvil cell. The thermodynamic region 0 < P < 1.5 GPa and 120 < T < 380 degrees C has been explored. The data analysis shows that for rising pressure the optical gap does not appreciably changes, while a relevant increase of the absorption occurs. A significant gap closure as a function of T has been found, but it is not sufficient to justify the appearance of the semiconductor-to-metal transition previously observed at approximate to 650 degrees C in fluid I-2. On the basis of the present results, a new hypothesis about the mechanism underlying the semiconductor-to-metal transition is proposed and discussed. Finally, the advantages of using an Infrared Synchrotron Radiation source for further measurements at higher pressure and temperature are briefly discussed.