Talk:ARPES

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Help with this template Comments: edit – history – watch – refresh First off, thank you for taking the time to initiate this article. It is an important contribution to Wikipedia, and it's about time someone undertook this task! I have many suggestions for this article. I hope you will find them helpful. With regard to content, I have some suggestions (in no particular order): 1. The introduction should mention the photoelectric effect, and it should link to the photoelectric effect article. The PE effect is simple physics that will be accessible to a broad audience. 2. "The technique" section also does not even mention the PE effect. In fact, it mentions nothing about how the experiments are actually carried out. There are two main classes of ARPES analyzers: hemispherical and time-of-flight. Explain physically how each of these work. How are the energies resolved? How are the momenta resolved? (See the next suggestion). 3. The section on kinematics fails to show how ARPES determines the k vector of the electron wavefunction. k parallel to the sample face is determined via the emission angle and kinetic energy. k perpendicular to the sample face can be extracted by varying the photon energy. 4. There are multiple ways to model the photoemission process. The simplest is the "3-step" model, which is essentially a sudden approximation model. The three steps are excitation, transport to the surface, and escape to vacuum. This is an intuitive and simple model that does not involve propagators. It is easy for people to visualize, and it merits being mentioned. 5. ARPES is a sub-experiment of PES (photoemission or photoelectron spectroscopy). Similar and related techniques include XPS (x-ray photoelectron spectroscopy) and XPD (x-ray photoelectron diffractometry). These should be mentioned, and links should be provided to other articles, where available. 6. Most ARPES is carried out at synchrotron beamline facilities using very far-UV and soft x-ray photon energies. New experiments are beginning to use low photon energies (particularly from lasers) in the 6 - 8 eV range. This increases bulk sensitivity and reduces background scattering. It also increases momentum and energy resolution and reduces broadening due to final state effects. It may now be the case that ARPES is finally observing data that is very close to the unadulterated spectral function, allowing, for instance, for extraction of the many-body electron self-energy (see Norman et al, PRB, 60, 7585 (1999)). These new low-photon energy experiments may merit some mention. See, for example, Koralek et al, PRL, 96, 017005 (2006). Stylistically, this article should avoid the "royal 'we'". Additionally, there is some awkward language and a spattering grammatical errors. 128.138.96.194 18:52, 4 December 2007 (UTC)

I'm trying to improve and expand this article about ARPES technique. Any help will be welcome!--Neburzaragoza 20:35, 24 July 2007 (UTC)

[edit] Pictures

• I'm deleting the picutres from this article, Electron_analyser.JPG, Arpes_beamline.JPG , Arpes_spectra1.JPG and Arpes_spectra.JPG, because I don't have anymore the permission of the author to publish the in wikipedia.org.

I hope very soon somebody could upload some and give a visual exemple of a ARPES mesurement --Neburzaragoza 23:24, 11 September 2007 (UTC)

• I put them again in the article. I had the definitive permission to publish the pictures of all the authors : A. Damascelli, Zhi-Xun Shen and D. Bonn. I have also change two, in order to have a better approch of the apres mesurements --Neburzaragoza 18:40, 14 September 2007 (UTC)

[edit] Suggestions for improvement

First off, thank you for taking the time to initiate this article. It is an important contribution to Wikipedia, and it's about time someone undertook this task! I have many suggestions for this article. I hope you will find them helpful.

With regard to content, I have some suggestions (in no particular order):

1. The introduction should mention the photoelectric effect, and it should link to the photoelectric effect article. The PE effect is simple physics that will be accessible to a broad audience.

2. "The technique" section also does not even mention the PE effect. In fact, it mentions nothing about how the experiments are actually carried out. There are two main classes of ARPES analyzers: hemispherical and time-of-flight. Explain physically how each of these work. How are the energies resolved? How are the momenta resolved? (See the next suggestion). Also, it might be worth mentioning how spin detectors work.

3. The section on kinematics fails to show how ARPES determines the k vector of the electron wavefunction. k parallel to the sample face is determined via the emission angle and kinetic energy. k perpendicular to the sample face can be extracted by varying the photon energy.

4. There are multiple ways to model the photoemission process. The simplest is the "3-step" model, which is essentially a sudden approximation model. The three steps are excitation, transport to the surface, and escape to vacuum. This is an intuitive and simple model that does not involve propagators. It is easy for people to visualize, and I think it merits being mentioned. Perhaps we can explain that the sudden approximation means that the wavefunction does not change as the electron is photoemitted. As long as experiments operate in a regime where the sudden approximation is valid, then it is possible to interpret the data simplisticly to arrive at the actual wavefunction that the electron had when it was still in the sample. Then again, maybe this is a minor point for most readers.

5. ARPES is a sub-experiment of PES (photoemission or photoelectron spectroscopy). Similar and related techniques include XPS (x-ray photoelectron spectroscopy) and XPD (x-ray photoelectron diffractometry). These should be mentioned, and links should be provided to other articles, where available.

6. Most ARPES is carried out at synchrotron beamline facilities using very far-UV and soft x-ray photon energies. New experiments are beginning to use low photon energies (particularly from lasers) in the 6 - 8 eV range. This increases bulk sensitivity and reduces background scattering. It also increases momentum and energy resolution and reduces broadening due to final state effects. It may now be the case that ARPES is finally observing data that is very close to the unadulterated bulk spectral function, allowing, for instance, for extraction of the many-body electron self-energy (see Norman et al, PRB, 60, 7585 (1999)). These new low-photon energy experiments may merit some mention. See, for example, Koralek et al, PRL, 96, 017005 (2006).

7. The section on resolution could probably be incorporated into another section. Also, the values are understated by today's standards. The Scienta R4000 has sub-meV resolution, I believe. I think this is also true for the latest Specs spectrometers. Of course, resolution is always improving, so any value stated today will be too high again in just a couple years!

Stylistically, this article should avoid the "royal 'we'". Additionally, there is some awkward language and a spattering of grammatical errors.

Again, thank you. I hopefully will be able to help with this article as time allows.

Firstorderapproximation (talk) 18:31, 6 December 2007 (UTC)