Photoemission study of no chemisorption on Pd (111) using synchrotron radiation with energy of 30–130 eV

Abstract

A synchrotron radiation study of NO chemisorption on Pd(111) was carried out at room temperature in the hv = 30–130 eV range which covers the “Cooper minimum” of Pd4d electrons. The relative enhancement in photoemission sensitivity of the NO-derived 4 σ, 5 σ + 1π and 2π molecular orbitals was dramatic at hv = 120–130 eV, and NO was confirmed to chemisorb in molecular form on the surface at room temperature. The bonding shifts of the 5 σ and 1π orbitals were found to be smaller than 0.2 eV. The 2π level showed a significant bonding shift of 0.7-1.9 eV, suggesting that the unpaired electron in the 2π orbital is mainly responsible for the chemisorption bonding through a charge transfer mechanism; i.e., electron donation from the 2π up-spin level into the metal and simultaneous back-donation into the down-spin 2π state from the metal.