Spectral set: Difference between revisions

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[[Image:Copper K Rontgen.png|thumb | Atomic levels involved in copper Kα and Kβ emission]]
In [[X-ray spectroscopy]], '''K-alpha''' emission lines result when an electron transitions to the innermost "K" shell (principal quantum number 1) from a 2p orbital of the second or "L" shell (with principal quantum number 2). The line is actually a doublet, with slightly different energies depending on [[spin-orbit interaction]] energy between the electron spin and the orbital momentum of the 2p orbital. K-alpha is typically by far the strongest X-ray spectral line for an element bombarded with energy sufficient to cause maximally intense X-ray emission.
 
The analogous K-alpha spectra line in hydrogen is known as [[Lyman alpha]]; however because of hydrogen's small nuclear charge, this line is in the ultraviolet, not the X-ray range. See [[Siegbahn notation]] for the newer [[IUPAC]]-recommended spectral notation system.  
 
An example of K-alpha lines are those seen for iron as iron atoms radiating X-rays spiralling into a [[black hole]] at the center of a galaxy [http://arxiv.org/abs/astro-ph/0405337]. For such purposes, the energy of the line is adequately calculated to 2-digit accuracy by the use of [[Moseley's law]]: <math>E = (10.2 eV)\left(Z-1\right)^2</math>, where Z is the atomic number. For example, K-alpha for iron (Z = 26) is calculated in this fashion as 10.2 eV (25)<sup>2</sup> = 6.38 keV energy. For astrophysical purposes, [[Doppler effect|Doppler]] and other effects (such as gravitational broadening) show the iron line to no better accuracy than 6.4 keV. [http://www.journals.uchicago.edu/cgi-bin/resolve?id=doi:10.1086/340992&erFrom=-6703307617883835216Guest]
 
== Values of Transition Energies ==
*Values of different kinds of transition energies like K<sub><math>\alpha</math></sub>, K<sub><math>\beta</math></sub>, L<sub><math>\alpha</math></sub>, L<sub><math>\beta</math></sub> and so on  for different elements can be found in the NIST X-Ray Transition Energies Database.<ref>[[NIST]] X-Ray Transition Energies Database [http://physics.nist.gov/PhysRefData/XrayTrans/index.html]</ref>
*K-alpha emission values for hydrogen-like and helium-like ions can be found on Table 1-5 of the LNBL X-Ray Data Booklet <ref>[[Lawrence Berkeley National Laboratory]] X-Ray Data Booklet [http://xdb.lbl.gov/]</ref>
 
==References==
{{reflist}}
 
[[Category:Spectroscopy]]
[[Category:X-rays]]
[[Category:Quantum chemistry]]
[[Category:Astronomical spectroscopy]]
[[Category:Atomic physics]]

Latest revision as of 14:37, 26 September 2012

Atomic levels involved in copper Kα and Kβ emission

In X-ray spectroscopy, K-alpha emission lines result when an electron transitions to the innermost "K" shell (principal quantum number 1) from a 2p orbital of the second or "L" shell (with principal quantum number 2). The line is actually a doublet, with slightly different energies depending on spin-orbit interaction energy between the electron spin and the orbital momentum of the 2p orbital. K-alpha is typically by far the strongest X-ray spectral line for an element bombarded with energy sufficient to cause maximally intense X-ray emission.

The analogous K-alpha spectra line in hydrogen is known as Lyman alpha; however because of hydrogen's small nuclear charge, this line is in the ultraviolet, not the X-ray range. See Siegbahn notation for the newer IUPAC-recommended spectral notation system.

An example of K-alpha lines are those seen for iron as iron atoms radiating X-rays spiralling into a black hole at the center of a galaxy [1]. For such purposes, the energy of the line is adequately calculated to 2-digit accuracy by the use of Moseley's law: E=(10.2eV)(Z1)2, where Z is the atomic number. For example, K-alpha for iron (Z = 26) is calculated in this fashion as 10.2 eV (25)2 = 6.38 keV energy. For astrophysical purposes, Doppler and other effects (such as gravitational broadening) show the iron line to no better accuracy than 6.4 keV. [2]

Values of Transition Energies

  • Values of different kinds of transition energies like Kα, Kβ, Lα, Lβ and so on for different elements can be found in the NIST X-Ray Transition Energies Database.[1]
  • K-alpha emission values for hydrogen-like and helium-like ions can be found on Table 1-5 of the LNBL X-Ray Data Booklet [2]

References

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  1. NIST X-Ray Transition Energies Database [3]
  2. Lawrence Berkeley National Laboratory X-Ray Data Booklet [4]