diff --git a/applications/NXxas_new.nxdl.xml b/applications/NXxas_new.nxdl.xml
index e6864bdb83..449859d32f 100644
--- a/applications/NXxas_new.nxdl.xml
+++ b/applications/NXxas_new.nxdl.xml
@@ -110,7 +110,7 @@
Excited element
-
+
Excited electron level
@@ -121,7 +121,7 @@
The emission lines are described as a list of names of the form
*"INITIAL-FINAL"* where *INITAL* and *FINAL* are electron levels
- as listed for :ref:`here </NXelectron_level/name-field>`.
+ as listed for :ref:`here </NXxray_level/name-field>`.
diff --git a/base_classes/NXelectron_level.nxdl.xml b/base_classes/NXelectron_level.nxdl.xml
deleted file mode 100644
index 97ed107ee6..0000000000
--- a/base_classes/NXelectron_level.nxdl.xml
+++ /dev/null
@@ -1,61 +0,0 @@
-
-
-
-
- TODO ??? levels of electrons in atoms.
-
-
- TODO Name of the atomic orbital in IUPAC or X-ray notation.
-
- The corresponding atomic notation *nlj* is also given, where *n* the principal quantum number,
- *l* the orbital angular momentum quantum number (expressed with letters s, p, d, ...) and *j = l + s*
- (*s=±½* the spin quantum number).
-
-
- - 1s1/2
- - 2s1/2
- - 2p1/2
- - 2p3/2
- - 3s1/2
- - 3p1/2
- - 3p3/2
- - 3d3/2
- - 3d5/2
- - 4s1/2
- - 4p1/2
- - 4p3/2
- - 4d3/2
- - 4d5/2
- - 4f5/2
- - 4f7/2
-
-
-
diff --git a/base_classes/NXxray_level.nxdl.xml b/base_classes/NXxray_level.nxdl.xml
new file mode 100644
index 0000000000..7ef382915b
--- /dev/null
+++ b/base_classes/NXxray_level.nxdl.xml
@@ -0,0 +1,90 @@
+
+
+
+
+
+ The electronic state of an atom occurring as initial or final state of a process
+ involving the absorption or emission of X-ray radiation.
+
+ The energy of an atom with one missing electron is referred to as an *X-ray level*. It is a
+ multi-electronic state which occurs as a result of the photoemission of one electron.
+
+
+
+ The *X-ray level* name as recommended by `IUPAC <https://doi.org/10.1002/xrs.1300200308>`_.
+
+ The corresponding :math:`nl_{j}^{-1}` notation of the electron configuration is also provided:
+
+ * *n* the principal quantum number (shell)
+ * *l* the orbital angular momentum quantum number (subshell, expressed with letters *s=0*, *p=1*, *d=2*, ...)
+ * *j = l + s* the total angular momentum (spin-orbit splitting)
+ * *s=±½* the spin angular momentum quantum number
+ * :math:`^{-1}` refers to one missing electron
+
+ The subshell energy levels are split due to the unpaired electron left behind after photoemission of
+ one electron, that may have a parallel or antiparallel alignment to the orbital momentum.
+
+
+ - :math:`1s^{-1}`
+ - :math:`2s^{-1}`
+ - :math:`2p_{1/2}^{-1}`
+ - :math:`2p_{3/2}^{-1}`
+ - :math:`3s^{-1}`
+ - :math:`3p_{1/2}^{-1}`
+ - :math:`3p_{3/2}^{-1}`
+ - :math:`3d_{3/2}^{-1}`
+ - :math:`3d_{5/2}^{-1}`
+ - :math:`4s^{-1}`
+ - :math:`4p_{1/2}^{-1}`
+ - :math:`4p_{3/2}^{-1}`
+ - :math:`4d_{3/2}^{-1}`
+ - :math:`4d_{5/2}^{-1}`
+ - :math:`4f_{5/2}^{-1}`
+ - :math:`4f_{7/2}^{-1}`
+ - :math:`5s^{-1}`
+ - :math:`5p_{1/2}^{-1}`
+ - :math:`5p_{3/2}^{-1}`
+ - :math:`5d_{3/2}^{-1}`
+ - :math:`5d_{5/2}^{-1}`
+ - :math:`5f_{5/2}^{-1}`
+ - :math:`5f_{7/2}^{-1}`
+ - :math:`5g_{7/2}^{-1}`
+ - :math:`5g_{9/2}^{-1}`
+ - :math:`6s^{-1}`
+ - :math:`6p_{1/2}^{-1}`
+ - :math:`6p_{3/2}^{-1}`
+ - :math:`6d_{3/2}^{-1}`
+ - :math:`6d_{5/2}^{-1}`
+ - :math:`6f_{5/2}^{-1}`
+ - :math:`6f_{7/2}^{-1}`
+
+
+