Band gap and index of refraction of CsH to 251 GPa

Abstract

Optical transmission and reflectivity measurements were made on CsH to 251 GPa. The index of refraction for CsH, obtained from reflectivity measurements, varied linearly with fractional density from 1.28 at zero pressure to 3.21 at 251 GPa. The band gap, estimated by the absorption edge, was found to be 4.4 eV at zero pressure and closed to 1.9 eV at 251 GPa.