Storage Ring Measurement of the C IV Recombination Rate Coefficient

The low-energy C IV dielectronic recombination (DR) rate coefficient associated with 2s → 2p Δn = 0 excitations of this lithium-like ion has been measured with high-energy resolution at the heavy-ion storage ring TSR of the Max-Planck-Institut für Kernphysik in Heidelberg, Germany. The experimental procedure and especially the experimental detection probabilities for the high Rydberg states produced by the recombination of this ion are discussed in detail. From the experimental data a Maxwellian plasma rate coefficient is derived with ±15% systematic uncertainty and parameterized for ready use in plasma-modeling codes. Our experimental result especially benchmarks the plasma rate coefficient below 10⁴ K where DR occurs predominantly via C III (1s²2p4l) intermediate states and where existing theories differ by orders of magnitude. Furthermore, we find that, to within our systematic uncertainty of 15%, the total dielectronic and radiative C IV recombination can be represented by the incoherent sum of our DR rate coefficient and the radiative recombination rate coefficient of Pequignot and coworkers.