Improved Laboratory Transition Probabilities for Nd ii and Application to the Neodymium Abundances of the Sun and Three Metal‐poor Stars

Abstract

Radiative lifetimes, accurate to � 5%, have been measured for 168 odd-parity levels of Nd ii using laser-induced fluorescence. The lifetimes are combined with branching fractions measured using Fouriertransform spectrometry to determine transition probabilities for over 700 lines of Nd ii. This work is the largest-scale laboratory study to date of Nd ii transition probabilities using modern methods. This improved data set is used to determine Nd abundances for the Sun and three metal-poor giant stars with neutroncapture enhancement: CS 22892� 052, HD 115444, and BD +17 � 3248. In all four stars the line-to-line scatter is considerably reduced from earlier published results. The solar photospheric abundance is determined to be log � ðNd Þ¼ 1:45 � 0:01ð� ¼ 0:05Þ, which is in excellent agreement with meteoric data. The ratio of Nd/Eu is virtually identical in all three metal-poor Galactic halo stars. Furthermore, the newly determined stellar Nd abundances, in comparison with other heavy neutron-capture elements, are consistent with an r-process–only origin early in the history of the Galaxy. These more accurate Nd abundance determinations might help to constrain the predicted solar system r-process abundances, and suggest other elements for further neutron-capture abundance studies. Subject headings: atomic data — stars: abundances — Sun: abundances On-line material: machine-readable tables