High-resolution measurement of the dielectronic recombination of fluorinelike selenium ions

We have measured the dielectronic recombination cross section of Se{sup 25+} ions at center-of-mass energies from 1 to 1800 eV using merged electron and ion beams in the Heidelberg heavy-ion Test Storage Ring (TSR). All dielectronic resonances involving changes of {Delta}{ital N}=0 and {Delta}{ital N}=1 of the core principal quantum number {ital N} are covered with high-energy resolution (ranging from {lt}0.6 eV at {lt}90 eV to {approx_equal}6 eV at 1600 eV). A strong contribution of {Delta}{ital N}=1 Rydberg resonances at 1200{endash}1700 eV is observed. The results are compared with isolated-resonance intermediate-coupling calculations of the cross section. Good agreement is found for the {Delta}{ital N}=0 and the low-lying {Delta}{ital N}=1 resonances. For the {Delta}{ital N}=1 Rydberg series the resonant pattern continues to be well reproduced by theory, whereas the total energy-integrated cross section significantly exceeds the theoretical prediction. From experimental and theoretical results rate coefficients for isotropic plasma temperatures between 100 and 2000 eV are also derived. {copyright} {ital 1996 The American Physical Society.}