Absolute measurements of the energies of resonance lines in heliumlike vanadium on an electron-beam ion trap are reported. The $1s2p{}^1{P}_1\to {1s}^2,$ $1s2p{}^3{P}_2\to {1s}^2$ $(1s2p{}^3{P}_1\to {1s}^2$ and $1s2p{}^3{P}_0\to {1s}^2)$ blend and $1s2s{}^3{S}_1\to {1s}^2$ transitions are $5205.10\pm 0.14\mathrm{eV},$ $5189.12\pm 0.21\mathrm{eV},$ $5180.22\pm 0.17\mathrm{eV},$ and $5153.82\pm 0.14\mathrm{eV},$ 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 $Z=19\mathrm{}–31$ range. The measurement of the $1s2s{}^3{S}_1\to {1s}^2$ transition is also sensitive to the $1s2s{}^3{S}_1$ QED contribution at the 40% level. The intensity of the strong $1s2p{}^3{P}_1\to {1s}^2$ component of the blend compared to the total blend intensity is $94\%\pm 12\%.$ This is in accord with current theoretical predictions but disagrees with an earlier reported ratio.

• Received 14 February 2000

DOI:https://doi.org/10.1103/PhysRevA.62.042501