Photoelectron spectroscopy of laser-excited surfaces by synchrotron radiation

Long, J. P.; Itchkawitz, B. S.; Kabler, M. N.

doi:10.1364/josab.13.000201

Cited by 19 publications

(30 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As indicated by the fitted solid lines, the energy shift as well as the energy broadening approach a linear dependence on N c / d 0 at high electron densities. In this regime, relation ͑1͒, the model proposed by Long et al, 37 overestimates the simulated space-charge-induced energy broadening by a factor of 3. At low electron densities ͑N c / d 0 Ͻ 10 4 e − / mm͒, the energy broadening deviates from the linear relationship and approaches some finite value of ϳ10 meV.…”

Section: B Core-level Spectroscopymentioning

confidence: 86%

“…The first model was put forward by Long et al 37 The sample is assumed to be a sphere of diameter d 0 and the photoelectrons are assumed to reside within an expanding spherical shell of negligible thickness, implying that the pulse duration is much smaller than the transit time of the fastest electrons to the detector. For the energy spread, in this case the difference between the energy gained by an electron at the leading edge and the energy lost by an electron at the trailing edge of the shell, the authors find that…”

Section: A Simple Models For the Energy Broadeningmentioning

confidence: 99%

“…However, for today's synchrotron and laser light sources these parameters may differ by orders of magnitude, so that via the material specific photoemission process each set of parameters will result in a distinct initial photoelectron distribution in real and momentum spaces. Although previous efforts have performed simple numerical simulations 9,38 or have used simple analytical models 21,34,37,40 with quite some success to explain space-charge effects for a few typical experimental conditions, they have also yielded open questions related to, for instance, the exact functional dependence of the spectral broadening on the number of electrons per pulse, the role of mirror charges in the sample, the neglect of mutual Coulomb interaction in the photoelectron cloud in simulations, and the loss of angular resolution due to space-charge effects. In addition, previous studies do not fully clarify the validity range of the simple models, nor do they provide a few rough rules of thumb for the practitioner.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Vacuum space-charge effects in solid-state photoemission

et al. 2009

View full text Add to dashboard Cite

Solid-state photoemission spectroscopy relies to a large part on pulsed photon sources: third-generation synchrotron-radiation sources and ultrafast laser systems in particular. Especially when the photon pulses are intense, Coulombic repulsion between the emitted electrons will be a limiting factor for photoemission experiments aiming at highest energy and angle resolutions. In the present work, the propagation of the photoelectron cloud to the detector is studied with a full N-body numerical simulation. The influence of various parameters, in particular number of electrons per pulse, source size, pulse duration, kinetic-energy and emission-angle distributions as well as presence of mirror charges in the sample, is investigated in detail. Previous experimental results obtained with various picosecond and femtosecond light sources are successfully reproduced and the general resolution limits of solid-state photoemission using pulsed photon sources are explored. The results are potentially important for the design and interpretation of photoemission experiments with next-generation light sources, such as free-electron lasers and high-harmonic generation sources.

show abstract

Section: B Core-level Spectroscopymentioning

confidence: 86%

Section: A Simple Models For the Energy Broadeningmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Vacuum space-charge effects in solid-state photoemission

et al. 2009

View full text Add to dashboard Cite

show abstract

“…Some two-photon-photoemission experiments combining lasers and synchrotron light sources have been reported [17]. The pulse length of the electron bunches in the synchrotron limits the time resolution and the synchronization between laser and synchrotron constitutes a difficult task [18].…”

Section: Methodsmentioning

confidence: 99%

Time‐resolved two‐photon photoemission

Fauster¹

2003

Solid‐State Photoemission and Related Methods

View full text Add to dashboard Cite

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

show abstract

“…The combined SR-laser system 18,21 was located at beamline X24C at the National Synchrotron Light Source, Brookhaven National Laboratory. There the pump-laser source was a copper-vapor laser (hϭ2.43 eV) operating at 6 kHz and configured with competing cavities to produce 5-ns pulses full width at half maximum ͑FWHM͒.…”

Section: Methodsmentioning

confidence: 99%

Excited-state photoelectron spectroscopy of excitons inC60and photopolymerizedC60
Long
¹
,
Chase
²
,
Kabler
³

2001
Phys. Rev. B
Self Cite
16
0
7
0
View full text Add to dashboard Cite

Laser-excited states in films of pristine C 60 and photopolymerized C 60 (pp-C 60 ) prepared in ultrahigh vacuum have been characterized in situ with pump-probe photoelectron spectroscopy using both synchrotron radiation and picosecond laser sources. Photoelectron spectra of singlet (S 1 ) and triplet (T 1 ) excitons overlap because of vibrational broadening in the photoemission final state. The spectra have been individually isolated in pp-C 60 with time-resolved methods and are split by 0.33 eV. Signals from pristine C 60 are weaker but are spectroscopically similar. The origin for exciton transitions for both C 60 and pp-C 60 is found to be properly located near the maximum of the highest occupied molecular orbital. Increasing excitation density favors T 1 production over S 1 such that, at high exciton concentrations, T 1 states predominate, even at times much shorter than the unimolecular intersystem crossing time, measured to be ϳ2.5 ns for pp-C 60 at 81 K. A weaker photoemission band located ϳ0.5 eV above S 1 is also observed and is attributed to charge carriers and/or charge-transfer excitons.

show abstract

Photoelectron spectroscopy of laser-excited surfaces by synchrotron radiation

Cited by 19 publications

References 45 publications

Vacuum space-charge effects in solid-state photoemission

Vacuum space-charge effects in solid-state photoemission

Time‐resolved two‐photon photoemission

Excited-state photoelectron spectroscopy of excitons inC60and photopolymerizedC60
Long
¹
,
Chase
²
,
Kabler
³

2001
Phys. Rev. B
Self Cite
16
0
7
0
View full text Add to dashboard Cite

Contact Info

Product

Resources

About

Photoelectron spectroscopy of laser-excited surfaces by synchrotron radiation

Cited by 19 publications

References 45 publications

Vacuum space-charge effects in solid-state photoemission

Vacuum space-charge effects in solid-state photoemission

Time‐resolved two‐photon photoemission

Excited-state photoelectron spectroscopy of excitons inC60and photopolymerizedC60Long1, Chase2, Kabler3 2001Phys. Rev. BSelf Cite16070View full textAdd to dashboardCite

Contact Info

Product

Resources

About

Excited-state photoelectron spectroscopy of excitons inC60and photopolymerizedC60
Long
¹
,
Chase
²
,
Kabler
³

2001
Phys. Rev. B
Self Cite
16
0
7
0
View full text Add to dashboard Cite