Measurement and Calculation of Absolute Single and Multiple Charge Exchange Cross Sections for Fe^g+ Ions Impacting H₂O

Journal Article · Wed Sep 01 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/722/1/435· OSTI ID:993798

Simcic, J ^[1]; Schultz, David Robert ^[2]; Mawhorter, R J ^[3]; Greenwood, J B ^[4]; Winstead, C ^[5]; McKoy, B V ^[5]; Smith, S J ^[6]; Chutjian, A ^[1]

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1. Jet Propulsion Laboratory/Caltech
2. ORNL
3. Pomona College
4. Queen's University, Belfast
5. California Institute of Technology, Pasadena
6. Indiana Wesleyan University, Marion

Charge exchange (CE) plays a fundamental role in the collisions of solar- and stellar-wind ions with lunar and planetary exospheres, comets, and circumstellar clouds. Reported herein are absolute cross sections for single, double, triple, and quadruple CE of Fe^q+ (q = 5-13) ions with H₂O at a collision energy of 7q keV. One measured value of the pentuple CE is also given for Fe⁹⁺ ions. An electron cyclotron resonance ion source is used to provide currents of the highly charged Fe ions. Absolute data are derived from knowledge of the target gas pressure, target path length, and incident and charge-exchanged ion currents. Experimental cross sections are compared with new results of the n-electron classical trajectory Monte Carlo approximation. The radiative and non-radiative cascades following electron transfers are approximated using scaled hydrogenic transition probabilities and scaled Auger rates. Also given are estimates of cross sections for single capture, and multiple capture followed by autoionization, as derived from the extended overbarrier model. These estimates are based on new theoretical calculations of the vertical ionization potentials of H₂O up to H₂O¹⁰⁺.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC); Work for Others (WFO)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 993798
• Journal Information: Astrophysical Journal, Vol. 722, Issue 1; ISSN 0004--637X
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
AUTOIONIZATION
CHARGE EXCHANGE
CLOUDS
COMETS
CROSS SECTIONS
DATA
ELECTRON CYCLOTRON-RESONANCE
ELECTRON TRANSFER
ION SOURCES
IONIZATION POTENTIAL
TARGETS