Image-state electron scattering on flat Ag/Pt (111) and stepped Ag/Pt (997) metal surfaces
Abstract
Angle-resolved ultrafast two-photon-photoemission is used to investigate image-state-electron lifetimes on two bimetallic surfaces, Ag/Pt(111) and Ag/Pt(997) . This photoemission probe measures the relative dependence of image-electron dynamics on parallel electron momentum, k‖ , for flat and stepped surfaces. The n=1 and n=2 image states are identified by their k‖ -dependent energy values on the flat surface and for directions parallel and perpendicular to the step array. A weakly dispersive feature was observed in the energy distribution curves in the direction across steps. We show that the ratio of the n=2/n=1 state lifetimes on the flat surface at k‖=0 is increased over its value for single-crystal Ag(111) due to the Pt substrate. The k‖ dependence of scattering time of the n=1 state on both flat and stepped surfaces can be fitted to a function T1-Sk‖2 ; on the flat surface S is equal to 205±45fsÅ2 , on the stepped surface the measured values for S are 110±30fsÅ2 and 40±30fsÅ2 in the direction parallel and perpendicular to the step edges, respectively. These results are compared to those on flat and stepped Cu(100) surfaces.
- Publication:
-
Physical Review B
- Pub Date:
- April 2005
- DOI:
- 10.1103/PhysRevB.71.165424
- Bibcode:
- 2005PhRvB..71p5424S
- Keywords:
-
- 73.20.At;
- 78.47.+p;
- 79.60.-i;
- Surface states band structure electron density of states;
- Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter;
- Photoemission and photoelectron spectra