The electronic structures of $\mathrm{Ti}{\mathrm{H}}_x$, $\mathrm{Zr}{\mathrm{H}}_x$, and $\mathrm{Hf}{\mathrm{H}}_x$ have been studied using photoelectron spectroscopy and synchrotron radiation. Structures in the metal $d$-derived band within ∼3 eV of the Fermi level $E_F$ and in the bonding band (∼3-10 eV below $E_F$) are compared with theory. In each dihydride, the bonding band center falls at -5.5 eV, at approximately the same energy as previously observed for the dihydrides of Sc and Y. Changes in the emission features near $E_F$ and at -7 eV have been observed in samples bridging the $\mathrm{fcc}\to \mathrm{fct}$ distortion in $\mathrm{Zr}{\mathrm{H}}_x$, $1.63\le x\le 1.94$. The changes at $E_F$ demonstrate the Jahn-Teller effect for the electronic states of $\mathrm{Zr}{\mathrm{H}}_x$. The binding energies of the Ti $3p$, Zr $4p$, Hf $5p$, and Hf $4f$ cores are observed to be greater than in the elemental metals, consistent with charge transfer to the hydrogen site.

• Received 9 September 1980

DOI:https://doi.org/10.1103/PhysRevB.23.1692