Field-Emission Studies of Electronic Energy Levels of Adsorbed Atoms

摘要: The relative changes in the total energy distribution of field-emitted electrons upon adsorption single atoms have been measured for alkaline-earth (Ba, Sr, and Ca) on several crystal planes tungsten. expected perturbations due to tunneling resonance through an atomic "virtual level" at various positions Fermi surface half-widths $\ensuremath{\Gamma}$ is demonstrated by a simple one-dimensional calculation. energy-dependent structure current-enhancement factor adsorbate has interpreted tunneling-resonance model yield shapes levels." ground-state $^{1}S$ $6{s}^{2}$ level Ba broadened half-width ${\ensuremath{\Gamma}}_{S}=0.75$ eV shifted upward $\ensuremath{\Delta}{E}^{S}=0.95$ eV. This causes it overlap mix with first two excited states: triplet $^{3}D$ $6s5d$ singlet $^{1}D$ $6s5d$. observed levels were not had ${\ensuremath{\Gamma}}_{D}=0.1$ Similarly, state Ca, $^{3}P$ $4s4p$, was $\ensuremath{\Delta}{E}^{3\mathrm{P}}\ensuremath{\approx}0.4$ width ${\ensuremath{\Gamma}}_{3\mathrm{P}}\ensuremath{\approx}0.3$ ($2\ensuremath{\Gamma}=\mathrm{FWHM}$). effect band substrate discussed.