title: Absolute measurement of the relativistic magnetic dipole transition energy in heliumlike argon.
abstract: The 1s2s (3)S(1)→1s(2) (1)S(0) relativistic magnetic dipole transition in heliumlike argon, emitted by the plasma of an electron-cyclotron resonance ion source, has been measured using a double-flat crystal x-ray spectrometer. Such a spectrometer, used for the first time on a highly charged ion transition, provides absolute (reference-free) measurements in the x-ray domain. We find a transition energy of 3104.1605(77) eV (2.5 ppm accuracy). This value is the most accurate, reference-free measurement done for such a transition and is in good agreement with recent QED predictions.
authors.affiliation: Laboratoire Kastler Brossel, Ecole Normale Supérieure, CNRS, Université Pierre et Marie Curie-Paris 6, Case 74, 4 Place Jussieu, F-75005 Paris, France.
authors.forename: Pedro
authors.initials: P
authors.lastname: Amaro
authors.forename: Sophie
authors.initials: S
authors.lastname: Schlesser
authors.forename: Mauro
authors.initials: M
authors.lastname: Guerra
authors.forename: Eric-Olivier
authors.initials: EO
authors.lastname: Le Bigot
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Isac
authors.forename: Pascal
authors.initials: P
authors.lastname: Travers
authors.forename: José Paulo
authors.initials: JP
authors.lastname: Santos
authors.forename: Csilla I
authors.initials: CI
authors.lastname: Szabo
authors.forename: Alexandre
authors.initials: A
authors.lastname: Gumberidze
authors.forename: Paul
authors.initials: P
authors.lastname: Indelicato