Theoretical and experimental lifetime and oscillator strength determination in singly ionized neodymium (Nd ii)

Abstract

Radiative lifetime measurements were performed with time‐resolved laser‐induced fluorescence techniques for 24 levels of Nd ii in the energy range 20 500–32 500 cm−1. For 17 levels, no previous experimental data exist. These results have allowed the testing of new theoretical calculations with the relativistic Hartree–Fock method taking configuration interactions and core‐polarization effects into account, and a satisfying agreement has been found for this complex ion. A new set of calculated oscillator strengths, accurate within a few per cent for the strongest transitions, is presented for 107 lines of astrophysical interest appearing in the wavelength range 358.0–1100.0 nm. These results will be useful to evaluate abundance values of neodymium in chemically peculiar stars in relation with cosmochronology.

Laser-induced breakdown spectroscopy for branching ratio and atomic lifetime measurements in singly-ionized neodymium and gallium

“…Our reported A-coefficients (labeled as WSU) for these eight transitions are in agreement with those from the University of Western Ontario [4], UW-Madison [19], as well as the Lund Institute of Technology [11]. The reported values from Western Ontario and Madison are experimentally determined values, combining measured lifetimes and branching ratios.…”

“…The chamber was evacuated by a mechanical vacuum pump (Varian DS-302) to achieve an ambient gas pressure of 7.7 mbar [11] with an argon buffer gas to help create optimal plasma conditions for atomic emission. When using pressures lower than atmosphere, argon buffer gas produces the highest plasma temperature, highest electron density, and highest emission intensity as compared to such gases as helium or nitrogen [21].…”

“…The major parameters which were investigated were emission intensity, signalto-noise ratio, and the measured Einstein A-coefficients and their discrepancy with previously reported A-coefficients [4,11,19]. The bottom-most region (region 4) of the plasma plume had signal intensities which were of the smallest magnitude (~500 A.U.)…”

“…This level has eight spontaneously decaying branches from 430 nm to 636 nm. Absolute emission intensities for these eight transitions were measured to determine branching ratios for comparison with previous studies using alternate methods and ion sources [4,11,19]. Using lifetimes determined experimentally by others, oscillator strengths were determined.…”

“…Experimentally, lifetimes and branching ratios in ions can be determined via multiple methods which can excite the necessary atomic transitions. Branching ratios are most frequently measured with fast ion beam-laser beam measurements [11] or Fourier Transform Spectroscopy (FTS) methods made with hollow cathode discharge tubes [12]. A large variety of techniques have been developed and utilized for lifetime measurements in the nanosecond region.…”