Electron-impact excitation and recombination into excited states of lithiumlike ions

Relative excitation rate coefficients of N i and O i are measured using a well-diagnosed Θ-pinch plasma. Levels of n=4 and 5 are included in the measurements for the first time. Experimental values are in satisfactory agreement with theoretical values. A method to deduce the recombination rate coefficient from the He-like ions is suggested from the observations of the effect of recombination on transitions originating from levels of principal quantum number n=4 and 5. Recombination rates of ∼${10}^{\mathrm{-}12}$ ${\mathrm{cm}}^3$ ${\mathit{s}}^{\mathrm{-}1}$ at 69 eV for N i and ∼${10}^{\mathrm{-}13}$ ${\mathrm{cm}}^3$ ${\mathit{S}}^{\mathrm{-}1}$ at 40 eV for O i are deduced. These rates are no larger than the known theoretical rates for radiative, three-body, and dielectronic recombination; charge exchange with hydrogen is suggested as possible explanation.