X-ray photoemission spectroscopy study of zirconium hydride

X-ray photoemission spectroscopy (XPS) measurements are reported for ZrH1.65 and Zr metal. The valenceband measurements are compared with available band-theory density-of-states calculations for the metal and hydride. The hydride spectrum differs significantly from the metal spectrum. Most important, a strong peak associated with hydrogen s electrons appears approximately 7 eV below the Fermi level. XPS measurements of Zr $4p$ core levels show a binding-energy shift of 1 eV between Zr metal and ZrH1.65. It is argued that this shift results from charge readjustment in the vicinity of the Zr site. With the addition of hydrogen, net charge must be transferred from the Zr site to the hydrogen site. A charge-density analysis based on simplified cluster calculations is presented.