Atomic transition probabilities for Dy I and Dy II

Summary form only given, as follows. Atomic transition probabilities for 915 spectral lines of neutral and singly ionized dysprosium are reported. Typical uncertainties are 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 beam, to determine these transition probabilities. Reference sets of Ar I and Ar II branching ratios are used in most of the work reported here to establish a radiometric calibration for the Fourier transform spectra 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.