Journal article

Publication year: 2004

Pages: 1185-1191

Journal: Astronomy & Astrophysics

Volume number: 421

Issue number: 3

ISSN: 0004-6361

Open access status: Green

DOI Link: https://doi.org/10.1051/0004-6361:20040380

Publisher: EDP Sciences

Abstract: 
The rate coefficient for radiative and dielectronic recombination of beryllium-like magnesium ions was measured with high resolution at the Heidelberg heavy-ion storage ring TSR. In the electron-ion collision energy range 0-207 eV resonances due to 2s --> 2p (DeltaN = 0) and 2s --> 3l (DeltaN = 1) core excitations were detected. At low energies below 0.15 eV the recombination rate coefficient is dominated by strong 1s(2) (2s 2p P-3) 7l resonances with the strongest one occuring at an energy of only 21 meV. These resonances decisively influence the Mg IX recombination rate coefficient in a low temperature plasma. The experimentally derived Mg IX dielectronic recombination rate coefficient (+/-15% systematical uncertainty) is compared with the recommendation by Mazzotta et al. (1998, A&AS, 133, 403) and the recent calculations by Gu (2003, ApJ, 590, 1131) and by Colgan et al. (2003, A&A, 412, 597). These results deviate from the experimental rate coefficient by 130%, 82% and 25%, respectively, at the temperature where the fractional abundance of Mg IX is expected to peak in a photoionized plasma. At this temperature a theoretical uncertainty in the 1s(2) (2s2 p P-3) 7/ resonance positions of only 100 meV would translate into an uncertainty of the plasma rate coefficient of almost a factor 3. This finding emphasizes that an accurate theoretical calculation of the Mg IX recombination rate coefficient from first principles is challenging.

Harvard Citation style: Schippers, S., Schnell, M., Brandau, C., Kieslich, S., Müller, A. and Wolf, A. (2004) Experimental MgIX photorecombination rate coefficient, Astronomy & Astrophysics, 421(3), pp. 1185-1191. https://doi.org/10.1051/0004-6361:20040380

APA Citation style: Schippers, S., Schnell, M., Brandau, C., Kieslich, S., Müller, A., & Wolf, A. (2004). Experimental MgIX photorecombination rate coefficient. Astronomy & Astrophysics. 421(3), 1185-1191. https://doi.org/10.1051/0004-6361:20040380