Field enhanced dielectronic recombination of lithiumlike Ti-19 and Ni25+ ions

Within a series of systematic measurements of the dielectronic recombinatio n (DR) of Lithiumlike ions in the presence of external fields we have deter mined the absolute recombination rates of Ti19+ and Ni25+ ions. In both cas es the electron energy range covers all DR resonances attached to 2s --> 2p (1/2) and 2s --> 2P(3/2) Deltan = 0 core excitations. The experimental reso lution permits the study of the field effects for the two 2p(j)nl series of Rydberg DR resonances separately. For both the Ti19+ and the Ni25+ ions th e electric field induced enhancement is by factors of up to 1.8 stronger fo r the 2P(3/2) series than for the 2p(1/2) series. Moreover, we find that th e magnitude of the field induced DR rate enhancement becomes smaller as the nuclear charge increases. The dependence of the DR rate coefficient on mag netic fields in an E x B field configuration, that was only recently establ ished by theory and experiment, is also found for Ti19+ whereas for Ni25+ a change of the magnetic field over the range 42-80 mT did not significantly influence the DR rate enhancement induced by the electric field.