Measurement of effective dielectronic recombination rates for Fe ix, x, and xi

Effective rate coefficients for dielectronic recombination of Fe-ix, -x, and -xi ions at electron densities in the range of 3 × ${10}^{16}$ ${\mathrm{cm}}^{-3\mathrm{}}$ and electron temperatures up to 220 eV, were deduced from the time histories of emission lines in a small $\theta$-pinch plasma. The iron impurity in the hydrogen plasma was introduced by a laser puffing method. The intensities of lines from these ionization stages were measured as functions of time and interpreted by means of a time-dependent corona ionization-recombination model. A one-dimensional computer code, which takes into account the radial variations of $T_e$ and $n_e$, was used for the simulation of time histories. The effective rate coefficients were found to be equal to or smaller than currently accepted theoretical values for low-density plasmas.