Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

High-precision measurements of n = 2 → n = 1 transition energies and level widths in He- and Be- like Argon Ions



Jorge Machado, Csilla Szabo-Foster, Jose Paulo Santos, Pedro Amaro, Mauro Guerra, Guojie Bian, Jean-Michel Isac, Paul Indelicato


We have performed a reference-free measurement of the transition energies of the 1s2p1P1 → 1s2 1S0 line in He-like argon, and of the 1s2s22p 1P1 → 1s22s2 1S0 line in Be-like argon ions. The highly-charged ions were produced in the plasma of an Electron-Cyclotron Resonance Ion Source. Both energy measurements have been performed with an accuracy better than 2.0ppm, using a double flat-crystal spectrometer, without reference to any theoretical or experimental energy. The 1s2s22p 1P1 → 1s22s2 1S0 transition measurement is the first reference-free measurement for this core-excited transition. The 1s2p 1P1 → 1s2 1S0 transition measurement confirms recent measure- ment performed at the Heidelberg EBIT. The width measurement in He-like transition provide test of a radiative decay without Auger channels. In the case of the Be-like argon transition, the width results from the sum of a radiative channel and three main Auger channels. We have also performed ulticonfiguration Dirac-Fock (MCDF) calculations of transition energies and rates and done an extensive comparison with theory and other experimental data. Agreement with theory is excellent in both cases.
Physical Review A (Atomic, Molecular and Optical Physics)


Highly charged ions, He-like argon, Be-like argon, level widths, transition energies


Machado, J. , Szabo-Foster, C. , Santos, J. , Amaro, P. , Guerra, M. , Bian, G. , Isac, J. and Indelicato, P. (2018), High-precision measurements of n = 2 → n = 1 transition energies and level widths in He- and Be- like Argon Ions, Physical Review A (Atomic, Molecular and Optical Physics), [online], (Accessed May 21, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created March 25, 2018, Updated October 12, 2021