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

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 Fourier-transform 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 neutron-capture 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 ϵ(Nd) = 1.45 ± 0.01(σ = 0.05), 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.

[1]  K. Lodders.  Solar System Abundances and Condensation Temperatures of the Elements , 2003 .

[2]  C. Sneden,et al.  Genesis of the Heaviest Elements in the Milky Way Galaxy , 2003, Science.

[3]  E. A. Den Hartog,et al.  Radiative Lifetimes of Eu I, II, and III and Transition Probabilities of Eu I , 2002 .

[4]  T. Beers,et al.  First stars. I. The extreme r-element rich, iron-poor halo giant CS 31082-001 - Implications for the r-process site(s) and radioactive cosmochronology , 2002, astro-ph/0203462.

[5]  T. Beers,et al.  The Chemical Composition and Age of the Metal-poor Halo Star BD +17°3248 , 2002, astro-ph/0202429.

[6]  N. Grevesse,et al.  The composition of the solar photosphere , 2002 .

[7]  J. Lawler,et al.  Improved Laboratory Transition Parameters forEu II and Application to the Solar Europium Elemental and Isotopic Composition , 2001 .

[8]  J. Lawler,et al.  Atomic Transition Probabilities in Tb II with Applications to Solar and Stellar Spectra , 2001 .

[9]  J. Lawler,et al.  Experimental Radiative Lifetimes, Branching Fractions, and Oscillator Strengths for La II and a New Determination of the Solar Lanthanum Abundance , 2001 .

[10]  T. Beers,et al.  Neutron Capture Elements in s-Process-Rich, Very Metal-Poor Stars , 2001, astro-ph/0107040.

[11]  J. Lawler,et al.  Radiative lifetimes of Tb ii , 2001 .

[12]  E. A. Den Hartog,et al.  Experimental and Theoretical Radiative Lifetimes, Branching Fractions, and Oscillator Strengths for Lu I and Experimental Lifetimes for Lu II and Lu III , 2000 .

[13]  C. Sneden,et al.  Neutron-Capture Elements in the Early Galaxy: Insights from a Large Sample of Metal-poor Giants , 2000, astro-ph/0005188.

[14]  C. Sneden,et al.  The r-Process-enriched Low-Metallicity Giant HD 115444 , 1999, astro-ph/9910376.

[15]  J. Lawler,et al.  Atomic transition probabilities for Dy I and Dy II , 2000, IEEE Conference Record - Abstracts. 1999 IEEE International Conference on Plasma Science. 26th IEEE International Conference (Cat. No.99CH36297).

[16]  G. Wasserburg,et al.  Nucleosynthesis in asymptotic giant branch stars: Relevance for galactic enrichment and solar system formation , 1999 .

[17]  M. Busso,et al.  Neutron Capture in Low-Mass Asymptotic Giant Branch Stars: Cross Sections and Abundance Signatures , 1999, astro-ph/9906266.

[18]  E. A. Den Hartog,et al.  Spectroscopic Data for the 6it s6it p3 P1 level of Lu+ for the Determination of the Solar Lutetium Abundance , 1998 .

[19]  C. Cowley,et al.  A Re-Evaluation of the Abundance of Lutetium in the Sun , 1998 .

[20]  M. Tambasco,et al.  ENERGIES AND OSCILLATOR STRENGTHS FOR LITHIUMLIKE IONS , 1997 .

[21]  R. Kurucz.  Progress on Model Atmospheres and Line Data , 1997 .

[22]  Weiss Aw.  Multireferent superposition-of-configurations calculations of core-correlation effects on energy levels and oscillator strengths: Be and B+ , 1995 .

[23]  W. Whaling,et al.  Argon branching ratios for spectrometer response calibration , 1993 .

[24]  Ji,et al.  Beam-laser lifetime measurements for low-lying quartet states in Fe II. , 1992, Physical review. A, Atomic, molecular, and optical physics.

[25]  Jiayong,et al.  Lifetime measurement of the T=23 537 cm-1, J=9/2 odd-parity level in Nd II using time-resolved collinear fast-beam laser spectroscopy. , 1991, Physical review. A, Atomic, molecular, and optical physics.

[26]  N. Grevesse,et al.  Abundances of the elements: Meteoritic and solar , 1989 .

[27]  Chistopher Sneden,et al.  A Software Package for Microcomputer Reductions of Spectroscopic Data , 1987 .

[28]  S. Hashiguchi,et al.  Experimentally Determined Branching Ratios for Transitions in ArII , 1985 .

[29]  R. Hallin,et al.  Accurate Experimental Lifetimes of Excited Levels in Nd II , 1985 .

[30]  L. Ward.  Moderately accurate oscillator strengths from NBS intensities – a revision , 1985 .

[31]  Shuzo Hattori,et al.  Accurate oscillator strengths for neutral helium , 1984 .

[32]  D. Blackwell,et al.  Measurement of relative oscillator strengths for Cr I lines – I. Measures for transitions from levels a7S3 (0.00 eV), a5S2 (0.94 eV) and a5D0−4 (0.96−1.03 eV) , 1984 .

[33]  J. Blaise,et al.  Revised Interpretation of the Spectrum of Singly-Ionized Neodymium (Nd II) , 1984 .

[34]  C. Cowley,et al.  Moderately accurate oscillator strengths from NBS intensities – II , 1983 .

[35]  K. Danzmann,et al.  Argon branching ratios for spectral intensity calibration: a reply , 1982 .

[36]  V. Gorshkov,et al.  Lifetimes of excited levels of Nd I and Nd II. Oscillator strengths of the spectral lines of Nd I , 1982 .

[37]  D. Adams,et al.  Argon branching ratios for spectral-intensity calibration , 1981 .

[38]  M. Shallis,et al.  Precision measurement of relative oscillator strengths – VIII. Measures of Fe I transitions from levels a3F2–4 (1.49–1.61 eV) with an accuracy of 1 per cent , 1979 .

[39]  P. Ibbetson,et al.  Precision measurement of relative oscillator strengths – IV. Attainment of 0.5 per cent accuracy. Fe I transitions from levels a5 D0−4 (0.00−0.12 eV) , 1979 .

[40]  W. C. Martin,et al.  Atomic Energy Levels - The Rare-Earth Elements. The Spectra of Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, and Lutetium, , 1978 .

[41]  W. Whaling,et al.  Transition probabilities in Nd(II) and the solar neodymium abundance , 1977 .

[42]  A. Corney.  Atomic and laser spectroscopy , 1977 .

[43]  P. Ramanujam,et al.  Lifetimes of some excited states in the rare earths: La ii, Ce ii, Pr ii, Nd ii, Sm ii, Yb i, Yb ii, and Lu ii , 1975 .

[44]  C. Corliss,et al.  Tables of Spectral-Line Intensities: Part 1, Arranged by Elements , 1975 .

[45]  H. Holweger,et al.  The photospheric barium spectrum: Solar abundance and collision broadening of Baii lines by hydrogen , 1974 .

[46]  R. Zalubas,et al.  Atomic energy levels - The rare-Earth elements , 1974 .

[47]  C. Sneden.  The nitrogen abundance of the very metal-poor star HD 122563. , 1973 .

[48]  C. E. Moore,et al.  The Solar Spectrum 2935 Å to 8770 Å , 1966 .

[49]  B. Edĺen.  The Refractive Index of Air , 1966 .

[50]  J. Bearden,et al.  Atomic energy levels , 1965 .

[51]  C. Corliss,et al.  Experimental transition probabilities for spectral lines of seventy elements , 1962 .

[52]  C. Corliss,et al.  Tables of spectral-line intensities :: part II , 1961 .

[53]  William F. Meggers,et al.  Tables of spectral-line intensities , 1961 .

[54]  B. Edĺen,et al.  The Dispersion of Standard Air , 1953 .

[55]  Photometric atlas of the solar spectrum from [Lambda] 3612 to [Lambda] 8771 : with an appendix from [Lambda] 3332 to [Lambda] 3637 by M. Minnaert, G. F. W. Mulders, J. Houtgast , 1940 .