Photon energy dependence of the high resolution C 1<i>s</i>photoelectron spectrum of CO in the threshold region

Abstract

The C 1s photoelectron spectrum of CO has been measured with high resolution in the threshold region. The data exhibit hitherto unresolved vibrational structure on the C 1s main photoelectron line as well as new features in the satellite region. The vibrational energy of the ${\mathrm{CO}}^{+}$ ion is 301\ifmmode\pm\else\textpm\fi{}3 meV. The vibrational structure changes dramatically with photon energy due to the influence of the ${\mathrm{\ensuremath{\sigma}}}^{\mathrm{*}}$ shape resonance. The new satellite lines which are not present at high photon energies are attributed to conjugate shakeup processes.