Lifetimes, branching ratios, and transition probabilities in Co ii

The radiative lifetime of 14 levels in the $z^5$F, $z^5$D, and $z^5$G terms of Co ii have been measured with use of time-resolved laser fluorescence spectroscopy with a ${\mathrm{Co}}^{+}$-ion beam. Our lifetime values are shorter by 15–50 % than earlier results from beam-foil time-of-flight measurements. The lifetimes were converted to 41 individual transition probabilities with use of branching ratios measured on spectra recorded with the 1-m Fourier-transform spectrometer at the Kitt Peak National Observatory. On average our transition probabilities agree with those of Kurucz and Peytremann; for ΔS=1 transitions their calculated values are lower than our experimental results by a factor of ∼(1/4).