Direct Observation of Molecule-Substrate Antibonding States near the Fermi Level in Pd(110)-c(4×2)-Benzene

Evidence for a molecule-substrate hybridized state near the Fermi level $E_F$ is presented for Pd(110)- $c(4\times 2)$-benzene. Observed images of adsorbed benzene near $E_F$ by scanning tunneling microscopy consist of two elongated protrusions separated by a single nodal depression with $C_2$ symmetry. The existence of a benzene derived state near $E_F$ is also observed by metastable atom electron spectroscopy, and it is assigned to the antibonding states between the ${1e}_{1g}$ molecular orbital of benzene and the Pd $4d$ orbitals by ab initio molecular orbital calculations.