Threshold Measurements of Electron and Photon Collisions with Atoms and Small Molecules

  • George C. King
Chapter
Part of the Physics of Atoms and Molecules book series (PAMO)

Abstract

Something interesting usually happens when you excite a collision process close to its threshold. The energy of the incident particle (in the present case, an electron or a photon) is relatively small, ie just greater than the threshold energy of the reaction. Further, one or more electrons of very small energy (≤.01eV) can be produced. These conditions can have a profound influence on the collision. For example electron exchange can take place and electron-electron correlation effects can play a dominant role. Threshold excitation often leads to new and unexpected results. The present review deals with some of the characteristics of threshold excitation by electrons and photons and some of the aspects of the experimental techniques involved. As will be seen there are similarities betwen excitation by electrons and photons. For example the resonances observed in electron atom scattering have some similarities to the doubly excited states induced by photon excitation since both atomic systems consist of two electrons clinging to a positively charged core.

Keywords

Excitation Function Photon Beam Threshold Analyser Electron Impact Excitation Autoionizing State 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
This is a preview of subscription content, log in to check access.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Brunt J N H, Read F H and King G C, 1977 The realisation of high energy resolution using the hemispherical electrostatic energy selector in electron impact spectroscopy, J Phys E: Sci Instrum 10 134ADSCrossRefGoogle Scholar
  2. Buckman S J, Hammond P, King G C and Read F H 1983, High resolution electron impact excitation functions of metastable states of neon, argon, krypton, and xenon, J Phys B: Atom Molec Phys 16 4219ADSCrossRefGoogle Scholar
  3. Cooper J N, Fano U and Prats F 1963, Classification for two-electron excitation levels of helium, Phys Rev Letts 10 518ADSCrossRefGoogle Scholar
  4. Cvejanovid S and Read F H 1974a, Studies of threshold electron impact excitation of helium, J Phys B: Atom Molec Phys 7 1841ADSCrossRefGoogle Scholar
  5. Cvejanovid S and Read F H 1974b, A new technique for threshold excitation spectroscopy, J Phys B: Atom Molec Phys 7 1180ADSCrossRefGoogle Scholar
  6. Delwiche J, Hubin-Franskin M J, Guyon P M and Nenner I 1981, Autoionization of OCS by threshold photoelectron spectroscopy, J Chem Phys 74 4219ADSCrossRefGoogle Scholar
  7. Hall R I and Read F H 1984, Electron-Molecule Collisions, Ed I Shimamura and K Takayanagi (New York: Plenum) 35Google Scholar
  8. Hall R I, Cadez I, Schermann C and Tronc M 1977, Differential crossections for dissociative attachemtn in CO, Phys Rev A 15 599ADSCrossRefGoogle Scholar
  9. Hammond P, King G C, Jureta J and Read F H 1985, The threshold spectrum of carbon monoxide, J Phys B: Atom Molec Phys 18 2057ADSCrossRefGoogle Scholar
  10. Hammond P, Read F H and King G C 1988, J Phys B: Atom Molec Phys, to be published.Google Scholar
  11. Herrick D R and Kellman M E 1980, Novel supermultiplet energy levels for doubly excited He, Phys Rev A 21 481CrossRefGoogle Scholar
  12. Iachello F and Rau ARP 1981, Group theoretical approach to two-electron correlations in atoms, Phys Rev Lets 47 501ADSCrossRefGoogle Scholar
  13. King G C, Tronc M, Read F H and Bradford R C 1977, An investigation of the structure near the L2 , 3 edges of argon, the M4 , 5 edges of krypton and the N4 , 5, edges of xenon using electron impact with high resolution, J Phys B: Atom Molec Phys 10: 2479ADSCrossRefGoogle Scholar
  14. King G C, Zubek M, Rutter P M and Read F H 1987, A high resolution threshold elctron spectrometer for use in photoionization studies, J Phys E:Sci Instrum 20 440ADSCrossRefGoogle Scholar
  15. King G C, Zubek M, Rutter P M, Read F H, MacDowell A A, West J and Holland D M P 1988, A study of the threshold photoelectron spectrum of helium from the He+(n=2) state to the double ionization potential, J Phys B: Atom Molec Phys, to be publishedGoogle Scholar
  16. Klar H and Klar M 1980, An accurate treatment of two-electron systems using hyperspherical co-ordinates, J Phys B: Atom Molec Phys 13 1057ADSCrossRefGoogle Scholar
  17. Lipsky L, Anaria R and Connealy M J 1977, AE Data Nucl Data Tables 20 127ADSCrossRefGoogle Scholar
  18. Madden R P and Codling K 1963, New autionizing atomic energy levels in He, Ne and Ar, Phys Rev Letts 10 516ADSCrossRefGoogle Scholar
  19. Mazeau J, Greteau F, Joyez G, Reinhardt J and Hall R I 1972, Resonances in electron scattering from CO, J Phys B: Atom Molec Phys 5 1890ADSCrossRefGoogle Scholar
  20. Nesbet R K 1975, Vibrational calcualtions of electron impact excitation of He near the 23S and 21S thresholds, Phys Rev A 12 444ADSCrossRefGoogle Scholar
  21. Newman D S, Zubek M and King G C 1985, A study of resonance structure in mercury using metastable excitation by electron impact with high resolution, J Phys B: Atom Molec Phys 18 985ADSCrossRefGoogle Scholar
  22. Newman D S, Zubek M and King G C 1983, Metastable excitation measurements in CO and N2 by high resolution electron impact using a low work function detector, J Phys B: Atom Molec Phys 16 2247ADSCrossRefGoogle Scholar
  23. Niehaus A 1978, Electronic and Atomic Collisions, Ed G Watel (Amsterdam: North Holland) 185Google Scholar
  24. Peatman W B, Borne T B and Schlag E W 1969, Photoionization resonance spectra 1. Nitric oxide and benzene, Chem Phys Letts 3 492ADSCrossRefGoogle Scholar
  25. Peatman W B, Kasting G B and Wilson D 1975, The origin and elimination of spurious peaks in threshold electron photoionization spectra, J Elec Spec Rel Phen 7 233CrossRefGoogle Scholar
  26. Peatman W B, Gotcher B, Gurtler P, Koch E E and Saile V 1978, Transition probabilities at threshold for the photoionization of molecular nitrogen, J Chem Phys 69 2089ADSCrossRefGoogle Scholar
  27. Read F H 1976, The Physics of Electronic and Atomic Collisions, Ed J S Risley and R Geballe (Seattle: University of Washington Press) 176Google Scholar
  28. Zubek M, King G C, Rutter P M and Read F H 1988, Photoionization function measurements in Helium, J Phys B: Atom Molec Phys, to be publishedGoogle Scholar
  29. Zubek M 1986, A detector for metastable molecules with an adjustable detection threshold, J Phys E Sci Instrum 19 463.ADSCrossRefGoogle Scholar
  30. Zubek M and King G C 1987, The observation of a new metastable state in mercury and the measurement of its excitation function by high resolution electron impact, J Phys B: Atom Molec Phys 20 1135.ADSCrossRefGoogle Scholar
  31. Zubek M, King G C, Rutter P M and Read F H 1986a, Threshold photoionization studies in Xe and N2, J Phys B: Atom Molec Phys: to be published.Google Scholar

Copyright information

© Plenum Press, New York 1988

Authors and Affiliations

  • George C. King
    • 1
  1. 1.Department of Physics, Schuster LaboratoryManchester UniversityManchesterEngland

Personalised recommendations