Phonon reflectivity behavior in CsH and CsD at megabar pressures: Phonons in the near IR ( λ = 1 – 2 μm)

Abstract

Reflectivity at the diamond-sample interface was measured for CsH at P = 0, 102, 177 and 251 GPa and for CsD at 137 GPa in the energy range 0.5–2.5 eV. The expected isotope effect for phonons was found, confirming that the rise in reflectivity observed at high pressure and the near infrared as energy decrease is due to phonons and is not a plasma edge, which might also be expected in this pressure range for CsH. These are the first studies of phonon reflectivity in the diamond anvil cell to 2.5 Mbar and are the first high pressure phonon studies in any of the alkali hydrides.