Argon

Argon • Noble Gases

Primary XPS region: Ar2p
Overlapping regions: N/A
Binding energies of common chemical states:

Chemical state	Binding energy Ar2p
Implanted Ar	~243 eV

Experimental information

Ar is often detected in samples after argon ion sputtering, e.g., during a depth profile.
- It is more likely to be detected when using higher energy beams as this leads to implantation.
- At lower beam energies, the argon escapes through defects and damage in the crystal structure.

Interpretation of XPS spectra

Confirm assignment using Ar2s peak at 319eV.
Implanted argon may have apparent different binding energies, depending upon the nature of the matrix material.
- This may be a difference in work function rather than a true chemical shift.
Ar2p peak has clearly-spaced spin-orbit components (Δ=2.2eV, intensity ratio=0.512).

About this element

Symbol: Ar
Date of discovery: 1894
Name origin: Greek argos
Appearance: colorless gas
Discoverer: Ramsay, Rayleigh
Obtained from: air

Melting point: 83.8 K
Boiling point: 87.3 K
Density[kg/m³]: 1.784
Molar volume: 22.56 × 10^-6 m³/mol
Protons/Electrons: 18
Neutrons: 22
Shell structure: 2,8,8
Electron configuration: [Ne]3s23p6
Oxidation state: 0
Crystal structure: cubic face centered

Argon was discovered in 1894 by Lord Rayleigh and Sir William Ramsay, although Henry Cavendish suspected its existence over one hundred years earlier. This noble gas is chemically inert and is colorless and odorless in its liquid and gaseous forms. Argon makes up slightly less than 1% of the Earth’s atmosphere. There are no known stable chemical compounds containing argon. Due to its inert nature, argon is used in lighting, as a blanket in the manufacture of titanium, and in other applications needing a nonreactive medium.