Single-photon excitation of K $\alpha$ in heliumlike $\mathrm{Kr^{34+}}$ : Results supporting quantum electrodynamics predictions

We study two fundamental transitions from the ground state $^{1}$S$_{0}$ to $^{1}$P$_{1}$ (w line) and $^{3}$P$_{1}$ (y line) in heliumlike Kr$^{34+}$ by resonant single-photon excitation using an electron-beam ion trap and monochromatic x rays at PETRA III. Our results for the transition energies E(w)=13 114.47(14) eV and E(y)=13 026.15(14) eV are in excellent agreement with quantum electrodynamics calculations, but disagree for w with the average of the hitherto reported experimental results E$_{Lit}$(w)=13 115.15(17) eV. Independently of any energy calibration, we obtain a value E(w)/E(y)=1.006 780(7), also in consistency with predictions