The transitions 2s3S-2p3P of heavy helium-like ions: Fe XXV

We present an analysis of our wavelength measurements for the 1s2s 3S1-1s2p 3P2 transition of Fe XXV in beam-foil excited spectra at 6 MeV/u and 7 MeV/u. Results are compared with calculations including the non-relativistic energy, the one-electron Dirac energy, relativistic corrections, the Breit interaction and the one-electron Lamb shift corrections. The present wavelength measurement is sensitive to the Lamb shift contribution alone to a precision of +- 3%. We have detailed the limits of accuracy and the relative importance of the Zsup(-p)(αZ)sup(q) expansion terms of the transition energy for helium-like ions of heavy elements available now or in the near future. (orig.)