Experimental Transition Energies
The experimental portion of this data set was generated to provide the user
with a set of up-to-date accurate experimental x-ray energies. The reported
values have been corrected for all known errors and are determined using the
Recommended Values for the Fundamental Physical Constants: 1998
 and appropriate conversion factors. The
values are consistent with the International System of measurement.
The experimental energies included in this database were obtained using the
Directly measured transitions
First, a rather sparse network of x-ray transitions that are directly linked to
the International System of measurement was generated. All of these x-ray
transitions were measured using diffraction spectroscopy and crystals of known
lattice spacing. The crystal lattice spacings were determined using combined
x-ray and optical interferometry. These transitions are commonly referred to as
the optically based data.
Transitions linked to the directly measured transitions
In several cases it has been possible to expand the directly measured
transitions by considering earlier work in which several elemental spectra were
obtained using a common instrument platform and protocol, and at least one
member of the collection of lines reported belongs to our directly measured set.
In such cases it is relatively easy to re-scale the data reported so that it is
consistent with the directly measured transitions.
Transitions linked to directly measured gamma-ray lines
Some x-ray transitions (primarily in the high-Z region) have been
measured relative to gamma-ray transitions that have been determined using
calibrated crystals and diffraction spectroscopy (procedures identical to those
used to generate the optically based x-ray data). X-ray transitions obtained in
this fashion are also consistent with the directly measured transitions.
Re-scaling of existing earlier databases
In order to generate a more complete all-Z data set, we have used the
Bearden database for transitions not included in the above three categories.
Because the Bearden database  uses the Å* unit
(based on the WKα1
transition), it is relatively easy to re-scale these data so that they are
consistent with the optically based data.
The numbers in the reference column with the subscript "d" refer to
the experimental transition energies.