We use time-resolved laser-induced fluorescence to measure the lifetime of 186 Fe levels with energies between 25 900 and 60 758 cm . Measured emission branching fractions for these levels yield transition probabilities for 1174 transitions in the range 225-2666 nm. We find another 640 Fe transition probabilities by interpolating level populations in the inductively coupled plasma spectral source. We demonstrate the reliability of the interpolation method by comparing our transition probabilities with absorption oscillator strengths measured by the Oxford group [Blackwell et al., Mon. Not. R. Astron. Soc. 201, 595-602 (1982)]. We derive precise Fe level energies to support the automated method that is used to identify transitions in our spectra.

649their errors. Essentially the same weights were obtained independently from a consideration of the line widths and rates of drift in the various runs. If we take into account the small uncertainties of'gj(K) and gj(Cs) we obtain g /(Cr) = 2 (1.00081±0.00005). DISCUSSION AND CONCLUSIONOur measurements show that the ground state of Cr is a much "better" S state than was indicated by the less accurate optical value for gj. However, gj-(Cr) does differ by approximately 3 parts in 10 4 from g 8 , the pure electron spin g factor. This discrepancy can be due to several factors: (a) interaction terms in the radiative correction, 10,11 (b) nonradiative relativistic correction, 12 (c) diamagnetic correction, 13 and (d) perturbations due to higher states. The effects (a) and (b) have been calculated for some spectra with one or two 11 valence electrons and have been found to be much smaller than 3X10 -4 . No calculations are available for Cr which has six valence electrons. The diamagnetic correction (c) is negligible 13 (-2X10" 6 for Cr). The deviation of gj(Cr) from g s that has been found is indeed in the direction to be expected from a perturbation (d), but no quantitative conclusions can be drawn until the corrections (a) and (b) are known. 10 G. Breit, Phys. Rev. 39, 616 (1932). have pointed out the importance of the Be 8 (a,7)C 12 reaction in hot stars which have largely exhausted their central hydrogen. Hoyle 3 explains the original formation of elements heavier than helium by this process and concludes from the observed cosmic abundance ratios of 0 16 :C 12 :He 4 * On leave from the

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We report precision measurements by Fourier transform spectroscopy of the vacuum wavenumber, line width, and relative signal strength of 928 lines in the Ar I spectrum. Wavelength in air and classification of the transition are supplied for each line. A comparison of our results with other precision measurements illustrates the sensitivity of Ar I wavelengths to conditions in the light source.