Transition probabilities in Pr(II) and the solar praseodymium abundance

We have measured branching ratios for all of the known transitions from five levels in Pr⁺. We use the known mean lifetime of four of these levels to compute transition probabilities for 40 transitions. Five of our stronger lines are seen in the sun. We use the equivalent widths of Moore et al. and the solar model parameters of Righini and Rigutti to compute the photospheric Prabundance: log (N_Pr/N_H) + 12 = 0.66 ± 0.15. This value is a factor of ten lower than the most recent photospheric abundance measurement of Grevesse and Blanquet. The difference arises in part from the new transition probabilities, in part from the equivalent widths. We justify our use of widths from Moore et al. by comparing them with widths measured on the Preliminary Kitt Peak Solar Atlas.