J/ApJ/760/80 Fe^9+^ and Fe^10+^ cross-section measurements (Hahn+, 2012) ================================================================================ Storage ring cross-section measurements for electron impact single and double ionization of Fe^9+^ and single ionization of Fe^10+^. Hahn M., Becker A., Grieser M., Krantz C., Lestinsky M., Muller A., Novotny O., Repnow R., Schippers S., Spruck K., Wolf A., Savin D.W. =2012ApJ...760...80H ================================================================================ ADC_Keywords: Atomic physics Keywords: atomic data; atomic processes Abstract: We have measured electron impact ionization from the ground state of Fe^9+^ and Fe^10+^ over the relative electron-ion collision energy ranges 200-1900eV and 250-1800eV, respectively. The ions were confined in an ion storage ring long enough for essentially all metastable levels to radiatively relax to the ground state. For single ionization, we find a number of discrepancies between the existing theoretical cross sections and our results. The calculations appear to neglect some excitation-autoionization (EA) channels, particularly from n=3 to n' excitations, which are important near threshold, and those from n=2-->3 excitations, which contribute at about 650eV. Conversely, at higher energies the calculations appear to overestimate the importance of EA channels due to excitation into levels where n>=4. The resulting experimental rate coefficients agree with the most recent theory for Fe^9+^ to within 16% and for Fe^10+^ to within 19% at temperatures where these ions are predicted to form in collisional ionization equilibrium. We have also measured double ionization of Fe^9+^ forming Fe^11+^ in the energy range 450-3000eV and found that although there is an appreciable cross section for direct double ionization, the dominant mechanism appears to be through direct ionization of an inner shell electron producing an excited state that subsequently stabilizes through autoionization. Description: Measurements were carried out using the TSR heavy ion storage ring at the Max-Planck-Institut fur Kernphysik in Heidelberg, Germany. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 29 340 Fe^9+^ single ionization cross section (e^-^+Fe^9+^ -> Fe^10+^+2e^-^) table3.dat 29 318 Fe^10+^ single ionization cross section (e^-^+Fe^10+^ -> Fe^11+^+2e^-^) table5.dat 29 256 Fe^9+^ double ionization cross section (e^-^+Fe^9+^ -> Fe^11+^+3e^-^) -------------------------------------------------------------------------------- See also: J/A+A/565/A77 : Atomic data for FeIX (Del Zanna+, 2014) J/A+A/537/A22 : Atomic data for X-ray lines of FeVIII & FeIX (O'Dwyer+, 2012) J/ApJ/740/L52 : FeIX energy levels (Foster+, 2011) J/A+A/466/771 : H to Zn ionization rate coefficients (Dere+, 2007) J/A+AS/133/403 : Ionization balance for optically thin plasmas (Mazzotta+ 1998) J/A+AS/97/443 : Fluorescence for Be to Zn (Kaastra+ 1993) Byte-by-byte Description of file: table[235].dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 6 F6.1 eV E [205/3000] Collision energy 8- 18 E11.4 cm2 sigma Ionization cross section {sigma}_I_ 20- 29 E10.4 cm2 e_sigma Statistical uncertainty in {sigma}_I_ -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 29-Jul-2014