Recombination of W19+ ions with electrons: Absolute rate coefficients from a storage-ring experiment and from theoretical calculations

Experimentally measured and theoretically calculated rate coefficients for the recombination of W19+([Kr] 4d(10) 4f(9)) ions with free electrons (forming W18+) are presented. At low electron-ion collision energies, the merged-beam rate coefficient is dominated by strong, mutually overlapping, recombination resonances as already found previously for the neighboring charge-state ions W-18+ and W20+. In the temperature range where W19+ is expected to form in a collisionally ionized plasma, the experimentally derived recombination rate coefficient deviates by up to a factor of about 20 from the theoretical rate coefficient obtained from the Atomic Data and Analysis Structure database. The present calculations, which employ a Breit-Wigner redistributive partitioning of autoionizing widths for dielectronic recombination via multi-electron resonances, reproduce the experimental findings over the entire temperature range.