Experimental rate coefficients of F5+ recombining into F4

Recombination spectra of F5+ producing F4+ have been investigated with high-energy resolution, using the CRYRING heavy-ion storage ring. The absolute recombination rate coefficients are derived in the centre-of-mass energy range of 0−25 eV. The experimental results are compared with intermediate-coupling AUTOSTRUCTURE calculations for 2s−2p (△n = 0) core excitation and show very good agreement in the resonance energy positions and intensities. Trielectronic recombination with 2s2−2p2 transitions are clearly identified in the spectrum. Contributions from F5+ ions in an initial metastable state are also considered. The energy-dependent recombination spectra are convoluted with Maxwell-Boltzmann energy distribution in the 103−106 K temperature range. The resulting temperature-dependent rate coefficients are compared with theoretical results from the literature. In the 103−104 K range, the calculated data significantly underestimates the plasma recombination rate coefficients. Above 8 × 104 K, our AUTOSTRUCTURE results and plasma rate coefficients from elsewhere show agreement that is better than 25% with the experimental results.