Helium (He) X-ray absorption edges

The He $K$ edge is at 24.6 $eV$ . The tables list 1 absorption edge for helium; none lies between 100 $eV$ and 100 $keV$ , the range the lab can scan.

Atomic number: $Z = 2$
Molar mass: 4.0026 $g / mol$
Edges in the lab range: 0 of 1

Open helium in the lab

Both load helium as a pure sample with the formula $He$ . Density is retained from your current settings because these X-ray tables have no density. Enter your sample's density on the Sample page before planning a thickness. This edge is outside the lab range; the beamline shows only the available absorption background.

Absorption edges of helium

Energies, jump ratios and fluorescence yields as tabulated by Elam, Ravel and Sieber (2002). Scroll within the table to see every column.
Edge	Energy ( $eV$ )	Jump ratio	Fluorescence yield	In the lab
$K$	24.6	1	0	Outside range

Jump ratio is the photoabsorption just above the edge divided by the photoabsorption just below it. Fluorescence yield is the probability that a core hole in that shell decays by emitting an X-ray. Both are dimensionless. The lab can scan across edges strictly between 100 $eV$ and 100 $keV$ ; other edges are listed for reference. A listed edge with jump ratio 1 has no step for thickness planning.

Transmission, fluorescence or electron yield

No edge of helium lies between 100 $eV$ and 100 $keV$ , so the lab cannot model a measurement across one. Helium still adds to the absorption background of any sample that contains it.

Values from XrayDB 9.2 (Elam, Ravel and Sieber, 2002), released into the public domain. These isolated-atom tables do not include chemical shifts, XANES or EXAFS fine structure. Methods and data sources