Absolute measurement of the resonance lines in heliumlike vanadium on an electron-beam ion trap

Absolute measurements of the energies of resonance lines in heliumlike vanadium on an electron-beam ion trap are reported. The 1s2p¹P₁→1s², 1s2p³P₂→1s² (1s2p³P₁→1s² and 1s2p³P₀→1s²) blend and 1s2s³S₁→1s² transitions are 5205.10±0.14eV, 5189.12±0.21eV, 5180.22±0.17eV, and 5153.82±0.14eV, respectively. This agrees with recent theoretical calculations and the experimental precision lies at the same level as the current uncertainty in theory (0.1 eV). These measurements represent a 5.7--8% determination of the QED contribution to the transition energies and are the most precise measurements of heliumlike resonance lines in the $Z=19--31$ range. The measurement of the 1s2s³S₁→1s² transition is also sensitive to the 1s2s³S₁ QED contribution at the 40% level. The intensity of the strong 1s2p³P₁→1s² component of the blend compared to the total blend intensity is 94%±12%. This is in accord with current theoretical predictions but disagrees with an earlier reported ratio.