Observation of (3d4p -> 3d4d) and (3d4d -> 3d4f) transitions in the vacuumultraviolet spectra of calcium-like MnVI, FeVII and CoVIII

An analysis of the spectra of calcium-like Mn VI, Fe VII and Co VIII in the 550-1375 Angstrom wavelength region is reported following observations inv olving collision-based spectroscopy of ion-rare-gas collisions in an ion be am from an ECR ion source. The strongest lines were found to originate from 3d4s --> 3d4p and 3d4d --> 3d4f transitions in the spectra of Mn5+ and fro m 3d4p --> 3d4d and 3d4d --> 3d4f transitions in the spectra of Fe6+ and Co 7+ and were classified using multiconfiguration Hartree-Fock calculations a nd isoelectronic comparison. This permitted the location of the 3d4f H-3 le vels in these ions and established the energies of 14 of the levels in Fe V II and 13 of the levels in Co VIII of the 3d4d configuration for the first time.