Oscillator strengths for ultraviolet transitions in P II and Cu II

Analysis of ultraviolet absorption from the dominant ions in interstellar clouds provides information on the mineralogy of the solid material in space and on the synthesis of elements in our Galaxy and beyond. For the most part the spectra are acquired with the spectrometers on the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer. In order to convert the amount of absorption into an accurate abundance, determinations of oscillator strengths of sufficiently high quality are needed. We present our most recent beam-foil measurements in this area. Lifetimes, branching fractions, and oscillator strengths for all transitions within the P II multiplet at 1154 Å are compared with available results. Close agreement between our laboratory measurements and theoretical and semi-empirical calculations suggests a means for calibrating fast-beam instruments in the far ultraviolet. As for Cu II, our results for the line at 1358 Å provide further evidence for a short lifetime for the upper state of interest.