High-resolution C 1s and O 1s core-excitation spectroscopy of chemisorbed, physisorbed, and free CO

High-resolution soft-x-ray excitation spectra are reported for free CO, CO condensed on Au at 20 K, and CO chemisorbed on Ni(111). Chemisorption increases dramatically the widths of the C and O 1s2* transitions from < 0.2 to 2.2 eV for C 1s and from 1.15 to 3.5 eV for O 1s. Shifts of 0.3 eV (for C 1s) and 1.7 eV (for O 1s) towards lower energy are resolved for the first time and are explained in terms of the electronic distribution in excited CO. © 1984 The American Physical Society.