Journalartikel

Jahr der Veröffentlichung: 1997

Seiten: L115-L118

Zeitschrift: The Astrophysical Journal

Bandnummer: 489

Heftnummer: 1

ISSN: 0004-637X

Open Access Status: Green

DOI Link: https://doi.org/10.1086/310966

Verlag: American Astronomical Society

Abstract: 
At the low electron temperatures existing in photoionized gases with cosmic abundances, dielectronic recombination (DR) proceeds primarily via nl(j) --> nl(j)' excitations of core electrons (Delta n = 0 DR). At these temperatures, the dominant DR channel often involves 2p(1/2) --> 2p(3/2) fine-structure core excitations, which are not included in LS-coupling calculations or the Burgess formula. Using the heavy-ion storage ring at the Max-Planck-Institut fur Kernphysik in Heidelberg, Germany, we have verified experimentally for Fe XVIII that DR proceeding via this channel can be significant in relation to other recombination rates, especially at the low temperatures characteristic of photoionized gases. At temperatures in photoionized gases near where Fe XVIII peaks in fractional abundance, our measured Fe XVIII to Fe XVII Delta n = 0 DR rate coefficient is a factor of similar to 2 larger than predicted by existing theoretical calculations. We provide a fit to our measured rate coefficient for ionization equilibrium models. We have carried out new fully relativistic calculations using intermediate coupling, which include the 2p(1/2) --> 2p(3/2) channel and agree to within similar to 30% with our measurements. DR via the 2p(1/2) --> 2p(1/2) channel may also have spectroscopic implications, providing unique spectral signatures at soft X-ray wavelengths that could provide good electron temperature diagnostics.

Harvard-Zitierstil: Savin, D., Bartsch, T., Chen, M., Kahn, S., Liedahl, D., Linkemann, J., et al. (1997) Dielectronic recombination in photoionized gas: The importance of fine-structure core excitations, The Astrophysical Journal, 489(1), pp. L115-L118. https://doi.org/10.1086/310966

APA-Zitierstil: Savin, D., Bartsch, T., Chen, M., Kahn, S., Liedahl, D., Linkemann, J., Müller, A., Schippers, S., Schmitt, M., Schwalm, D., & Wolf, A. (1997). Dielectronic recombination in photoionized gas: The importance of fine-structure core excitations. The Astrophysical Journal. 489(1), L115-L118. https://doi.org/10.1086/310966