Atomic data for lighting and astrophysical applications: excited-state lifetimes and transition probabilities for rare-earth elements

Summary form only given. Because of the extremely rich spectra of rare-earth metals, a large volume of data for these elements is sought by the lighting industry for modelling of a new generation of High-Intensity Discharge lamps. In addition, the observation of rare-earths in the atmospheres of chemically peculiar stars means that this data is also of substantial interest to the astrophysics community. We are currently meeting this need with a combination of two experiments: excited-state lifetimes are obtained from laser-induced fluorescence measurements on a slow atomic/ionic beam, and branching fractions are obtained with a Fourier-transform spectrometer. These two sets of data are then combined to produce absolute transition probabilities (or, Einstein A-coefficients). This approach has been extremely fruitful in that, over the last year alone, 298 lifetimes and hundreds of transition probabilities have been measured to better than 5% and 10% accuracy, respectively, for neutral and singly-ionized thulium. (The strongest lines are emphasized in this first set of measurements.) Obtaining high-quality data of this nature has involved the development of an appropriate atomic beam source, as well as a careful understanding and elimination of a variety of systematic effects. Current work has yielded preliminary lifetime measurements on more than 400 levels of neutral and singly-ionized dysprosium, and will eventually continue with holmium.