Emission Lines

Characteristic radiation come from interactions between a high-energy particle, such as an electron, and an orbital electron in an atom. These interactions or collisions can, if the energy of the incoming electron is greater than the binding energy of the orbital electron, kick out the electron and leave a vacancy. An electron from a high energy level can move down to fill the vacancy. In the process, it gives up energy which is emitted in the form of a photon. For inner orbitals vacancies, these photons are generally in the x-ray regime. This process is schematically shown in the diagram below.

There are two notations used to refer to these transitions. Siegbahn notation has historically been used in the area of X-ray spectroscopy. Though still widely used, it has been replaced by a newer nomenclature recommended by the International Union of Pure and Applied Chemistry (IUPAC). It is referred to here as IUPAC notation. The correspondence between these two nomenclatures is shown in the table below.

Emission line translation

siegbahn	iupac
Kα1	K-L3
Kα2	K-L2
Kβ1	K-M3
Kβ3	K-M2
Lα1	L3-M5
Lα2	L3-M4
Lβ1	L2-M4
Lβ2	L3-N5
Lβ3	L1-M3
Lβ4	L1-M2
Lβ5	L3-O4,5
Lβ6	L3-N1
Lβ7	L1-O1
Lβ9	L1-M5
Ll	L3-M1
Mα1	M5-N7

For a more full listing see Table VIII.2 in IUPAC Report.

The energies of the x-rays from these transitions are unique to each element and are provided by a number of sources. This package makes use of those provided by the X-ray Data Booklet (October 2009). It provides energies in Table 1-3 as well as relative intensities. More precise transition energies can be found at the NIST X-ray transition energies database.

The full table of energies is provided in:

from roentgen import emission_lines

It is possible to search for all known characteristic lines in an energy range with:

>>> import astropy.units as u
>>> from roentgen.lines import get_lines
>>> lines = get_lines(5 * u.keV, 5.2 * u.keV)
>>> print(lines)
energy  z  transition intensity
  eV
------ --- ---------- ---------
5013.5  59        Lα2        11
5033.7  59        Lα1       100
5034.0  54        Lγ1         8
5042.1  57        Lβ1        60
5156.5  56     Lβ2,15        20
5177.2  63         Ll         4

If you are only interested in lines from a particular element, the search can be limited with:

>>> import astropy.units as u
>>> from roentgen.lines import get_lines
>>> ni_lines = get_lines(5 * u.keV, 10 * u.keV, element='Ni')
>>> print(ni_lines)
energy  z  transition intensity
  eV
------ --- ---------- ---------
7460.9  28        Kα2        51
8264.7  28      Kβ1,3        17
7478.2  28        Kα1       100