Relativistic Electron Correlation, Quantum Electrodynamics, and the Lifetime of the $1s^{2}2s^{2}2p{}^{2}P_{3/2}^o$ Level in Boronlike Argon

The lifetime of the ${\mathrm{Ar}}^{13+}$ $1s^{2}2s^{2}2p{}^{2}P_{3/2}^o$ metastable level was determined at the Heidelberg Electron Beam Ion Trap to be $9.573(4)(5)\mathrm{ms}(\mathrm{stat})(\mathrm{syst})$. The accuracy level of one per thousand makes this measurement sensitive to quantum electrodynamic effects like the electron anomalous magnetic moment (EAMM) and to relativistic electron-electron correlation effects like the frequency-dependent Breit interaction. Theoretical predictions, adjusted for the EAMM, cluster about a lifetime that is approximately $3\sigma$ shorter than our experimental result.

Figure 1

Experimental setup at the MPI-K EBIT.

Figure 2

Typical time-normalized decay curves for two series of measurements taken at different injection gas pressures, as reflected in the heights of the plateaus: (a) is for 1 s beam off time ($111.1\mu \mathrm{s}/\mathrm{\text{channel}}$), and (b) is for 200 ms beam off time ($50\mu \mathrm{s}/\mathrm{\text{channel}}$).

Figure 3

Lifetimes from decay curves (white circles: second series) taken for different run times (4–5 hours per data point) as a function of the ratio of the background level to the height of the plateau observed before turning off the electron beam [see Fig. 2b]. Our experimental value is compared to a CIDFS prediction [9].

Figure 4

Theoretical lifetimes [6, 7, 8, 9, 10, 11, 12, 13, 14] and (rightmost) the experimental result of Ref. 3. The EAMM contribution had been ignored in all theoretical calculations except for Refs. 7, 9.