Atomic transition probabilities for DyI and DyII

Atomic transition probabilities for 915 spectral lines of neutral and singly ionized dysprosium are reported. Typical uncertainties are less than or equal to +/-10%. Branching fractions, measured using the 1.0 m Fourier transform spectrometer (FTS) at the National Solar Observatory and the 2.0 m FTS at the National Institute of Standards and Technology (NIST), are combined with recently published radiative lifetimes, measured using time-resolved laser-induced fluorescence on a slow atomic/ionic be;lm, to determine these transition probabilities. Reference sets of Ar I and ArII branching ratios are used in most of the work reported here to establish a radiometric calibration for the Fourier transform spectral from the National Solar Observatory. A subset of the lines are also measured using the NIST FTS. Most importantly, an independent radiometric calibration based on standard lamps is used with the NIST FTS. The generally good agreement between these independent measurements provides additional confidence in the radiometric calibration and the accuracy of the measurements. (C) 2000 Elsevier Science Ltd. All rights reserved.