Two-photon photoemission via image-potential states

Giesen, K.; Hage, F.; Himpsel, F. J.; Riess, H. J.; Steinmann, W.

doi:10.1103/physrevlett.55.300

Cited by 314 publications

(108 citation statements)

References 27 publications

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“…The spectroscopy of surface states on the (1 1 1) surfaces of noble metals has been discussed in Sections 3 and 4. These occupied surface states can be seen as initial states in 2PPE [34,226] and linewidths comparable to regular photoelectron spectroscopy are observed [4,223,227,228]. An exception among the noble-metal surfaces is Pd (1 1 1) where the intrinsic surface state is unoccupied [229].…”

Section: Lifetimes Of Surface States On Clean Metal Surfacesmentioning

confidence: 95%

“…The topographical images monitor simultaneously the quality and structures of the surface area under investigation. Two-photon photoemission (2PPE) [4,34] in the time-resolved mode is the only technique which is able to study the decay in the time domain [35,36]. By combining this information with spectroscopic measurements a very detailed picture of the electron dynamics emerges.…”

Section: Introductionmentioning

confidence: 99%

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Decay of electronic excitations at metal surfaces

Echenique

Berndt

Chulkov

et al. 2004

Surface Science Reports

438

403

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Section: Lifetimes Of Surface States On Clean Metal Surfacesmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Decay of electronic excitations at metal surfaces

Echenique

Berndt

Chulkov

et al. 2004

Surface Science Reports

438

403

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“…In the pioneering work of Giesen et al [34] an unoccupied state 1.92 eV above E F was found for Ag(111) which could not be satisfactorily explained by any surface-or bulk-band-structure calculations. A later study showed, that there is no intermediate state involved, and assigned the transition to a two-photon excitation between two bulk sp-bands [35].…”

Section: Direct Bulk Transitionsmentioning

confidence: 99%

Time‐resolved two‐photon photoemission

Fauster¹

2003

Solid‐State Photoemission and Related Methods

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In this chapter time resolution will be introduced to photoemission experiments. This means not just a series of regular photoemission measurements to monitor the changes of a sample with time. In two-photon photoemission the time delay between the two photons is an additional experimental parameter which can be controlled with femtosecond resolution, i.e., on a time scale relevant for electronic processes. At the same time, the introduction of the second photon leads to the participation of an additional electronic state in the energy diagram for photoemission. Energy diagramIn Figure 8.1 the transition from initial state |1 to an intermediate state |2 after the absorption of the photon with energy hν a is shown. The second photon of energy hν b excites the electron out of the intermediate state into the final state |3 . If the final state energy E 3 is above the vacuum energy E vac , the electron might leave the surface and its kinetic energy E kin is measured with an electron energy analyzer. Obviously, the initial state has to be occupied, i.e., its energy E 1 should be below the Fermi energy E F . The intermediate state on the other hand has to be empty at first. In most cases it is desirable to keep the photon energy hν a below the work function Φ = E vac − E F , because this constitutes the threshold for one-photon photoemission. This applies also to the other photon, because processes with the role of the two photons interchanged are possible as well. Energy-resolved spectroscopyThe spectrum sketched at the right of Fig. 8.1 shows a peak at the final state energy E 3 . The cutoff at kinetic energy zero corresponds to the vacuum level E vac of the sample. Electrons with the highest energy after the absorption of the photons with energies hν a and hν b appear at kinetic energy E max − E vac = hν a + hν b − Φ. These limits are familiar from regular photoemission spectroscopy and can be used to determine the work function from the width of the spectrum. Similarly, the momentum k of the electron parallel to the surface is conserved for single-crystal surfaces. For electrons emitted at an angle ϑ with respect to the surface normal one obtainshk = √ 2mE kin sin ϑ. Umklapp processes would add reciprocal lattice vectors of the surface to the momentum conservation, but play usually no role in twophoton photoemission. One has to keep in mind that the kinetic energies are generally quite

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“…The projected bulk L-gap supports both the image potential states studied in the present research and the occupied surface state of A1 symmetry discovered by Gartland and Slagsvold. 90,86,109 This gap is s-p inverted, so that the standing-wave bulk wave functions of electrons whose energies are at the upper band edge are s-like funtions, while those at the lower band edge are are p-like. 31 ,20 The bulk electronic wavefunction of the lower bulk band edge at the center of the surface Brillouin zone is referred to as the ~, state.…”

Section: Reihl and Coworkersmentioning

confidence: 99%

“…27 ,31,66 For the purposes of the present experiment, the best value from the literature was judged to be 0.77 eV. 90 The effective mass of the n=l image potential state was determined by two-photon photoemission 65 The bulk and surface electronic states of the Ag(lll) L-gap described here are also diagrammed in Figure 10. Band mapping studies by angle-resol ved photoemission provide accurate, reliable information of the bulk band structure.…”

Section: Reihl and Coworkersmentioning

confidence: 99%

Image potential states at metal-dielectric interfaces

Merry¹

1992

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Two-photon photoemission via image-potential states

Cited by 314 publications

References 27 publications

Decay of electronic excitations at metal surfaces

Decay of electronic excitations at metal surfaces

Time‐resolved two‐photon photoemission

Image potential states at metal-dielectric interfaces

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