New measurements of spontaneous transition probabilities for beryllium-like ions

Abstract

The authors describe measurements of spectral line intensities for pairs of transitions having common upper levels and thus derive the branching ratios of their spontaneous radiative transition probabilities. These are then combined with the results of measurements of the radiative lifetimes of the upper levels by other authors to obtain values of the individual probabilities. Care was taken to avoid the effects of the trapping of resonance radiation, which could have invalidated the results. A particular feature of their measurements was the use of two spectrometers, spanning between them the wavelength range from less than 100 AA to over 7000 AA. The results are for transitions in N IV, O V and Ne VII and are given with a claimed accuracy of between 7 and 38%. These are compared with theoretically calculated values. Good agreement is found for some of the simpler electric dipole transitions. On the other hand, for some of the other transitions, which in certain cases are only possible because o configuration interaction, disparities between their measurements and theory are as large as a factor of five.