diff --git a/applications/NXxas_new.nxdl.xml b/applications/NXxas_new.nxdl.xml
new file mode 100644
index 0000000000..e6864bdb83
--- /dev/null
+++ b/applications/NXxas_new.nxdl.xml
@@ -0,0 +1,230 @@
+
+
+
+
+
+
+ The symbol(s) listed here will be used below to coordinate datasets with the same shape.
+
+
+ Number of energy data points
+
+
+ Number of electronic transitions
+
+
+
+ This is an application definition for X-ray absorption spectroscopy.
+
+
+
+ Official NeXus NXDL schema to which this file conforms. TODO: replace NXxas
+
+
+
+
+
+
+
+ -
+
+ TODO
+
+
+ -
+
+ TODO total or partial fluorescence yield
+
+
+ -
+
+ TODO high energy resolution fluorescence detected
+
+
+ -
+
+ TODO total or partial electron yield
+
+
+ -
+
+ TODO
+
+
+ -
+
+ TODO
+
+
+ -
+
+ TODO
+
+
+ -
+
+ TODO
+
+
+ -
+
+ TODO
+
+
+ -
+
+ TODO
+
+
+
+
+
+ Excited element
+
+
+
+ Excited electron level
+
+
+
+
+ Emission lines relevant when :ref:`mode </NXxas_new/ENTRY/mode-field>` is
+ `fluorescence yield` or `herfd`.
+
+ 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>`.
+
+
+
+
+
+
+ TODO
+
+
+
+
+
+ TODO
+
+
+
+
+
+ TODO
+
+
+
+
+
+
+ Descriptive name of the sample
+
+
+
+
+ Description on how :ref:`energy </NXxas_new/ENTRY/energy-field>`
+ and :ref:`intensity </NXxas_new/ENTRY/intensity-field>` were obtained
+ from the raw data.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ spacing between crystal planes of the reflection
+
+
+ Type or material of monochromating substance (Si, Ge, Multilayer).
+
+
+ Miller indices (hkl) values of nominal reflection
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ XAS intensity versus energy plot
+
+
+
+
+
+ Table like data structure common in the XAS domain.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
diff --git a/base_classes/NXelectron_level.nxdl.xml b/base_classes/NXelectron_level.nxdl.xml
new file mode 100644
index 0000000000..97ed107ee6
--- /dev/null
+++ b/base_classes/NXelectron_level.nxdl.xml
@@ -0,0 +1,61 @@
+
+
+
+
+ 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/NXelement.nxdl.xml b/base_classes/NXelement.nxdl.xml
new file mode 100644
index 0000000000..19237a8d29
--- /dev/null
+++ b/base_classes/NXelement.nxdl.xml
@@ -0,0 +1,171 @@
+
+
+
+
+ Definition of a chemical element.
+
+
+ For each symbol, the atomic number, common English name, and standard atomic weight are also given.
+
+
+ - Z=1, name="hydrogen", standard_atomic_weight=1.0078
+ - Z=2, name="helium", standard_atomic_weight=4.0026
+ - Z=3, name="lithium", standard_atomic_weight=6.94
+ - Z=4, name="beryllium", standard_atomic_weight=9.0122
+ - Z=5, name="boron", standard_atomic_weight=10.81
+ - Z=6, name="carbon", standard_atomic_weight=12.011
+ - Z=7, name="nitrogen", standard_atomic_weight=14.007
+ - Z=8, name="oxygen", standard_atomic_weight=15.999
+ - Z=9, name="fluorine", standard_atomic_weight=18.9984
+ - Z=10, name="neon", standard_atomic_weight=20.1797
+ - Z=11, name="sodium", standard_atomic_weight=22.9898
+ - Z=12, name="magnesium", standard_atomic_weight=24.305
+ - Z=13, name="aluminum", standard_atomic_weight=26.9815
+ - Z=14, name="silicon", standard_atomic_weight=28.085
+ - Z=15, name="phosphorus", standard_atomic_weight=30.9738
+ - Z=16, name="sulfur", standard_atomic_weight=32.06
+ - Z=17, name="chlorine", standard_atomic_weight=35.453
+ - Z=18, name="argon", standard_atomic_weight=39.948
+ - Z=19, name="potassium", standard_atomic_weight=39.0983
+ - Z=20, name="calcium", standard_atomic_weight=40.078
+ - Z=21, name="scandium", standard_atomic_weight=44.9559
+ - Z=22, name="titanium", standard_atomic_weight=47.867
+ - Z=23, name="vanadium", standard_atomic_weight=50.9415
+ - Z=24, name="chromium", standard_atomic_weight=51.996
+ - Z=25, name="manganese", standard_atomic_weight=54.938
+ - Z=26, name="iron", standard_atomic_weight=55.845
+ - Z=27, name="cobalt", standard_atomic_weight=58.9332
+ - Z=28, name="nickel", standard_atomic_weight=58.6934
+ - Z=29, name="copper", standard_atomic_weight=63.546
+ - Z=30, name="zinc", standard_atomic_weight=65.38
+ - Z=31, name="gallium", standard_atomic_weight=69.72
+ - Z=32, name="germanium", standard_atomic_weight=72.63
+ - Z=33, name="arsenic", standard_atomic_weight=74.9216
+ - Z=34, name="selenium", standard_atomic_weight=78.971
+ - Z=35, name="bromine", standard_atomic_weight=79.904
+ - Z=36, name="krypton", standard_atomic_weight=83.798
+ - Z=37, name="rubidium", standard_atomic_weight=85.4678
+ - Z=38, name="strontium", standard_atomic_weight=87.62
+ - Z=39, name="yttrium", standard_atomic_weight=88.9058
+ - Z=40, name="zirconium", standard_atomic_weight=91.224
+ - Z=41, name="niobium", standard_atomic_weight=92.9064
+ - Z=42, name="molybdenum", standard_atomic_weight=95.95
+ - Z=43, name="technetium", standard_atomic_weight=97.907
+ - Z=44, name="ruthenium", standard_atomic_weight=101.07
+ - Z=45, name="rhodium", standard_atomic_weight=102.906
+ - Z=46, name="palladium", standard_atomic_weight=106.42
+ - Z=47, name="silver", standard_atomic_weight=107.868
+ - Z=48, name="cadmium", standard_atomic_weight=112.414
+ - Z=49, name="indium", standard_atomic_weight=114.818
+ - Z=50, name="tin", standard_atomic_weight=118.71
+ - Z=51, name="antimony", standard_atomic_weight=121.76
+ - Z=52, name="tellurium", standard_atomic_weight=127.6
+ - Z=53, name="iodine", standard_atomic_weight=126.905
+ - Z=54, name="xenon", standard_atomic_weight=131.293
+ - Z=55, name="cesium", standard_atomic_weight=132.905
+ - Z=56, name="barium", standard_atomic_weight=137.327
+ - Z=57, name="lanthanum", standard_atomic_weight=138.905
+ - Z=58, name="cerium", standard_atomic_weight=140.116
+ - Z=59, name="praseodymium", standard_atomic_weight=140.908
+ - Z=60, name="neodymium", standard_atomic_weight=144.242
+ - Z=61, name="promethium", standard_atomic_weight=145.0
+ - Z=62, name="samarium", standard_atomic_weight=150.36
+ - Z=63, name="europium", standard_atomic_weight=151.96
+ - Z=64, name="gadolinium", standard_atomic_weight=157.25
+ - Z=65, name="terbium", standard_atomic_weight=158.925
+ - Z=66, name="dysprosium", standard_atomic_weight=162.5
+ - Z=67, name="holmium", standard_atomic_weight=164.93
+ - Z=68, name="erbium", standard_atomic_weight=167.259
+ - Z=69, name="thulium", standard_atomic_weight=168.934
+ - Z=70, name="ytterbium", standard_atomic_weight=173.045
+ - Z=71, name="lutetium", standard_atomic_weight=174.967
+ - Z=72, name="hafnium", standard_atomic_weight=178.49
+ - Z=73, name="tantalum", standard_atomic_weight=180.948
+ - Z=74, name="tungsten", standard_atomic_weight=183.84
+ - Z=75, name="rhenium", standard_atomic_weight=186.207
+ - Z=76, name="osmium", standard_atomic_weight=190.23
+ - Z=77, name="iridium", standard_atomic_weight=192.217
+ - Z=78, name="platinum", standard_atomic_weight=195.084
+ - Z=79, name="gold", standard_atomic_weight=196.967
+ - Z=80, name="mercury", standard_atomic_weight=200.592
+ - Z=81, name="thallium", standard_atomic_weight=204.383
+ - Z=82, name="lead", standard_atomic_weight=207.2
+ - Z=83, name="bismuth", standard_atomic_weight=208.98
+ - Z=84, name="polonium", standard_atomic_weight=209.0
+ - Z=85, name="astatine", standard_atomic_weight=210.0
+ - Z=86, name="radon", standard_atomic_weight=222.0
+ - Z=87, name="francium", standard_atomic_weight=223.0
+ - Z=88, name="radium", standard_atomic_weight=226.0
+ - Z=89, name="actinium", standard_atomic_weight=227.0
+ - Z=90, name="thorium", standard_atomic_weight=232.038
+ - Z=91, name="protactinium", standard_atomic_weight=231.036
+ - Z=92, name="uranium", standard_atomic_weight=238.029
+ - Z=93, name="neptunium", standard_atomic_weight=237.048
+ - Z=94, name="plutonium", standard_atomic_weight=239.052
+ - Z=95, name="americium", standard_atomic_weight=243.0
+ - Z=96, name="curium", standard_atomic_weight=247.0
+ - Z=97, name="berkelium", standard_atomic_weight=247.0
+ - Z=98, name="californium", standard_atomic_weight=251.0
+ - Z=99, name="einsteinium", standard_atomic_weight=252
+ - Z=100, name="fermium", standard_atomic_weight=257
+ - Z=101, name="mendelevium", standard_atomic_weight=258
+ - Z=102, name="nobelium", standard_atomic_weight=259
+ - Z=103, name="lawrencium", standard_atomic_weight=266
+ - Z=104, name="rutherfordium", standard_atomic_weight=267
+ - Z=105, name="dubnium", standard_atomic_weight=268
+ - Z=106, name="seaborgium", standard_atomic_weight=269
+ - Z=107, name="bohrium", standard_atomic_weight=270
+ - Z=108, name="hassium", standard_atomic_weight=269
+ - Z=109, name="meitnerium", standard_atomic_weight=278
+ - Z=110, name="darmstadtium", standard_atomic_weight=281
+ - Z=111, name="roentgenium", standard_atomic_weight=282
+ - Z=112, name="copernicium", standard_atomic_weight=285
+ - Z=113, name="nihonium", standard_atomic_weight=286
+ - Z=114, name="flerovium", standard_atomic_weight=289
+ - Z=115, name="moscovium", standard_atomic_weight=290
+ - Z=116, name="livermorium", standard_atomic_weight=293
+ - Z=117, name="tennessine", standard_atomic_weight=294
+ - Z=118, name="oganesson", standard_atomic_weight=294
+
+
+
+ The charge number *Z* of the atomic nucleus.
+
+
+
+ *Relative atomic mass* of the element in *amu*. It can be but is not restricted to the
+ *standard atomic weight* (using the natural abundance of isotopes).
+
+
+
+ The charge of the atom after ionic approximation of its heteronuclear bonds.
+
+