Dielectronic recombination of the Be-like ions: ${\mathrm{C}}^{2+}$,${\mathrm{N}}^{3+}$,${\mathrm{O}}^{4+}$, and ${\mathrm{F}}^{5+}$

The first measurements of dielectronic recombination rate coefficients associated with the 2s→2p excitation in the Be-like ions ${\mathrm{C}}^{2+}$, ${\mathrm{N}}^{3+}$, ${\mathrm{O}}^{4+}$, and ${\mathrm{F}}^{5+}$ are reported. We observed the amount of electron capture attending the passage of MeV/nucleon ion beams through a collinear, magnetically confined, space-charged-limited electron beam as a function of relative energy. The initial beams contained large numbers of ions for which the metastable states of the term 2s2p ${\mathrm{}}^3$P were populated, and the fraction of ions in the metastable states to those in the ground-state configuration 2$s^2$ were measured. The experimental rate coefficients are consistent in magnitude and shape with rates determined from distorted-wave calculations of the dielectronic recombination cross sections. The large fraction of metastable states in the initial ion beams had a pronounced effect on the shape and magnitude of the rate coefficients.