We have constructed a system for measuring the derivative spectra of very low energy photoelectrons using a lock-in technique. The main advantage of this system lies in determining the energy position of steps in the photoelectron spectra that arise from inelastic scattering of photoelectrons through the excitation of surface vibrational modes. With this system we have measured the derivative spectra of two isotopes, 12C16O and 13C18O adsorbed on Cu(001), and observed the small isotopic shift of ∼1 meV. This result demonstrates that one can precisely determine the vibrational energy of surface adsorbates by using the present measurement system.
- Lock-in technique
- Molecular-adsorbed metal surface
- Very low energy photoelectron spectroscopy
- Vibrational mode
ASJC Scopus subject areas
- Physics and Astronomy(all)