Effect of wave-function localization on the time delay in photoemission from surfaces
- Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States)
We investigate streaking time delays in the photoemission from a solid model surface as a function of the degree of localization of the initial-state wave functions. We consider a one-dimensional slab with lattice constant a{sub latt} of attractive Gaussian-shaped core potentials of width {sigma}. The parameter {sigma}/a{sub latt} thus controls the overlap between adjacent core potentials and localization of the electronic eigenfunctions on the lattice points. Small values of {sigma}/a{sub latt}<<1 yield lattice eigenfunctions that consist of localized atomic wave functions modulated by a ''Bloch-envelope'' function, while the eigenfunctions become delocalized for larger values of {sigma}/a{sub latt} > or approx 0.4. By numerically solving the time-dependent Schroedinger equation, we calculate photoemission spectra from which we deduce a characteristic bimodal shape of the band-averaged photoemission time delay: as the slab eigenfunctions become increasingly delocalized, the time delay quickly decreases near {sigma}/a{sub latt}=0.3 from relatively large values below {sigma}/a{sub latt}{approx}0.2 to much smaller delays above {sigma}/a{sub latt}{approx}0.4. This change in wave-function localization facilitates the interpretation of a recently measured apparent relative time delay between the photoemission from core and conduction-band levels of a tungsten surface.
- OSTI ID:
- 22095749
- Journal Information:
- Physical Review. A, Vol. 84, Issue 6; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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