Measurement of the lifetimes of the 4plevels in Ca ii using laser excitation of a fast beam

An excimer-pumped dye laser has been used to populate the 4p levels of Ca i i in a fast ion beam. The observed decay of the fluorescence intensity gives lifetimes of 7.07±0.07 and 6.87±0.06 ns for the J=(1/2 and J=(3/2 levels, respectively. These results represent a significant improvement in precision compared with our previously reported values. The lower uncertainties are the results of several improvements in our experimental procedure. The lifetimes obtained are in good agreement with previously published results. However, they differ significantly (about 9%) from the available theoretical estimates. The values for the lifetimes at the level of precision achieved in this experiment clearly indicate that previously published theoretical calculations do not adequately account for the transition probabilities from the ${}_{}{}^2{}_{}{}^{}\mathrm{P}$ levels of singly ionized calcium.