Within the past 2–3 years, various electron spectroscopy techniques, with electrons excited by either photons,1–6 electrons,7–9 or ions,10 have rapidly developed as probes of the electronic structure of surfaces, surface complexes, and surfaces covered with thin overlayers of metals. This development, which has as its underlying basis the surface sensitivity of electron emission in the ∠10–103 eV range (i.e., hot electron mean free paths are usually in the 3–30 A range), has accompanied parallel developments in electron energy analyzers and sources (e.g., synchrotron radiation).Alternative techniques for probing electron energy levels at solid surfaces include ultraviolet photoemission spectroscopy (UPS),1–6 x‐ray photoelectron spectroscopy (XPS),11 field emission spectroscopy (FES),12 electron‐energy‐loss spectroscopy (ELS),7,8 ion neutralization spectroscopy (INS),10 appearance potential spectroscopy (APS),9 etc. Each technique has its particular advantages and disadvantages. uv photoelectron and electr...