X-Ray Emission Cross Sections following Charge Exchange by Multiply-Charged Ions of Astrophysical Interest

S. OTRANTO, R. E. OLSON AND P. BEIERSDORFER

Belfast, Gran Bretaña

Conferencia; The 13th International Conference on the Physics of Hghly charged Ions; 2006

  State selective nl-electron capture cross sections calculated using the classical trajectory Monte Carlo (CTMC) model are presented for highly charged ions with Z = 6-10 colliding with atoms and molecules. These nl-cross sections are used to determine x-ray line emission following decay from high-lying states. The emission cross sections compare favorably with measurements made by Greenwood et al [1] for O8+ and Ne10+ at 3 keV/amu, and with recent x-ray emission cross sections measured with the EBIT machine at LLNL using O8+ and Ne9+,10+ on different targets at 10 eV/amu. The calculated cross sections are used to present an ab initio determination of the soft x-ray spectrum of comet C/Linear 1999 S4 that was observed by the Chandra X-ray Observatory [2]. In the Figure below, we show the obtained spectrum which was built by using the CTMC absolute line emission cross sections and the slow solar wind (SSW) ion abundances tabulated by Schwadron and Cravens [3]. The tabulated abundances ratio [C5+/C6+] = 0.66 was corrected to 1.03 according to the measurements of the Advanced Composition Explorer ACE/SWICS-SWIMS on the day of the measurement, July 14, 2000. We find excellent agreement between the Chandra satellite X-ray observations (crosses) and our predictions when using the corrected ion abundances  for the SSW  [4]. Calculations for spectra obtained from comet 2P/Encke will be presented at the meeting.   Work Supported by the Office of Fusion Energy Sciences, DOE.   References   [1] J. B. Greenwood, I. D. Williams, S. J. Smith and A. Chutjian, Phys. Rev. A 63, 062707 (2001). [2] C. M. Lisse, D. J. Christian, K. Dennerl, K. J. Meech, R. Petre, H. A. Weaver and S. J. Wolk, Science 292, 1343 (2001). [3] N. A. Schwadron and T. E. Cravens, Astrophys. J. 544, 558 (2000). [4] S. Otranto, R. E. Olson and P. Beiersdorfer, Phys. Rev. A 73, 022723 (2006).