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

摘要

Summary form only given. Because of the extremely rich spectra ofrare-earth metals, a large volume of data for these elements is soughtby the lighting industry for modelling of a new generation ofHigh-Intensity Discharge lamps. In addition, the observation ofrare-earths in the atmospheres of chemically peculiar stars means thatthis data is also of substantial interest to the astrophysics community.We are currently meeting this need with a combination of twoexperiments: excited-state lifetimes are obtained from laser-inducedfluorescence measurements on a slow atomic/ionic beam, and branchingfractions are obtained with a Fourier-transform spectrometer. These twosets of data are then combined to produce absolute transitionprobabilities (or, Einstein A-coefficients). This approach has beenextremely fruitful in that, over the last year alone, 298 lifetimes andhundreds of transition probabilities have been measured to better than5% and 10% accuracy, respectively, for neutral and singly-ionizedthulium. (The strongest lines are emphasized in this first set ofmeasurements.) Obtaining high-quality data of this nature has involvedthe development of an appropriate atomic beam source, as well as acareful understanding and elimination of a variety of systematiceffects. Current work has yielded preliminary lifetime measurements onmore than 400 levels of neutral and singly-ionized dysprosium, and willeventually continue with holmium