Optical absorption spectra of cesium iodide (CsI) at pressures up to 60 GPa

The optical absorption spectra of CsI single crystals have been measured in a diamond anvil cell at pressures up to 60 GPa. For the first time, the fine structure of the absorption edge of CsI has been observed at high pressures. The exciton effects are shown to be responsible for the fine structure of the absorption edge. The pressure of metallization of CsI is estimated to be approximately 110 GPa.