Intensity ratios of lines of the spin-changing "intersystem" multiplet of Si II (4P → 2Po) at 234 nm have been used to determine electron densities and temperatures in a variety of astrophysical environments. However, the accuracy of these diagnostic calculations have been limited by uncertainties associated with the available atomic data. We report the first laboratory measurement, using an ion-trapping technique, of the radiative lifetimes of the three metastable levels of the 3s3p2 4P term of Si II. Our results are 104 ± 16, 406 ± 33, and 811 ± 77 µs for lifetimes of the J = 1/2, 5/2, and 3/2 levels, respectively. A-values were derived from our lifetimes by use of measured branching fractions. Our A-values, which differ from calculated values by 30% or more, should give better agreement between modeled and observed Si II line ratios.
Original Publication Citation
Anthony G. Calamai, Peter L. Smith, and S. D. Bergeson. Transition probabilities for the 3s2 3p(2P0)-3s3p2(4P) intersystem lines of Si II. Astrophys. J. 415 (1), L59-L62 (1993).
BYU ScholarsArchive Citation
Calamai, Anthony G.; Smith, Peter L.; and Bergeson, Scott D., "Transition Probabilities for the 3s23p(2Po)–3s3p2(4P) Intersystem Lines of Si II" (1993). All Faculty Publications. 1826.
American Astronomical Society
Physical and Mathematical Sciences
Physics and Astronomy
© 1993 American Astronomical Society. This article is the Version of Record published by the American Astronomical Society in Astrophysical Journal in 1993, available online at http://adsabs.harvard.edu/full/1993ApJ...415L..59C
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