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

Abstract

We have measured the dielectronic recombination cross section of ${\mathrm{Se}}^{25+}$ 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 \ensuremath{\Delta}N=0 and \ensuremath{\Delta}N=1 of the core principal quantum number N are covered with high-energy resolution (ranging from 0.6 eV at 90 eV to \ensuremath{\approxeq}6 eV at 1600 eV). A strong contribution of \ensuremath{\Delta}N=1 Rydberg resonances at 1200--1700 eV is observed. The results are compared with isolated-resonance intermediate-coupling calculations of the cross section. Good agreement is found for the \ensuremath{\Delta}N=0 and the low-lying \ensuremath{\Delta}N=1 resonances. For the \ensuremath{\Delta}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. \textcopyright{} 1996 The American Physical Society.