CX DATABASE FOR COLLISION OF SLOW SINGLY AND MULTIPLY CHARGED IONS WITH NEUTRAL ATOMS AND MOLECULES OF RELEVANCE FOR FUSION

EDGE PLASMAS

Motivation

State-selective electron capture by slow multiply charged ions from atoms and molecules is considered an important process for the understanding and control of fusion- and astrophysical plasma properties. In colder plasma regions such collisions of ions with neutral

molecules can play an important role for the ionization balance and radiative energy loss and -cooling by impurity ions which are copiously present in these plasmas. The radiation loss from high-temperature plasmas is strongly dependent upon emission from impurity ions in moderately ionized states which in part can be formed by capture of electrons into excited states and decay by emitting characteristic radiation usually in the soft-x ray and VUV regions.

A number of experimental and theoretical investigations of cross sections for electron transfer processes involving slow multicharged ions have been made in the last ten years. Measured cross sections for electron capture have been found to be in satisfactory agreement with various theoretical calculations. In most cases, the total cross sections and also the principal quantum numbers of the electronic states of captured electrons can correctly be reproduced by models ranging from the simple classical over-barrier one to fully quantal calculations. In addition, experimental setups for measuring total and partial cross sections have been improved.

Charge exchange spectroscopy and photon-emission spectroscopy in the VUV, X-ray and visible regions are now well established techniques for such measurements, which are also of interest for impurity ion diagnostics. Time-of-flight (TOF) spectroscopy, translation energy spectroscopy (TES) and, in the very low energy range, state-selected ion flow-drift tube (SIFDT) mass spectrometers, multipole ion guiding systems and Penning quadrupole ion traps have been made available for measuring cross sections data with reasonable accuracy. Errors in such measurements resulting from unknown metastable state admixtures in ion beams produced from plasma multicharged ion sources (most notably Electron Cyclotron Resonance Ion Sources – ECRIS) are discussed in some theoretical and experimental papers. At low impact energy another source of uncertainty for electron transfer cross sections results from the repulsive interaction between post-collision partners which may be scattered into larger angles and thus a non-neglible fraction of charge-exchanged projectiles will not be collected.

Consequently, experimentally determined cross sections can become too small which influence becomes progressively more important toward lower impact energy. E.g., fusion-relevant charge-changing collisions of ” 1 keV C²⁺ and O²⁺ ions with H, H2, He and other atomic and molecular targets are affected by this errrors and the unknown metastable primary ion fractions causes further problems [8]. Finally, only few studies have been devoted to isotopic effect for H2 vs. D2, the possible influence of an initial vibrational excitation of such target molecules, etc.

General information about the database

In the following we present a data base containing measured and calculated cross sections for single electron capture in fusion-relevant collision systems involving slow singly and multiply-charged ions. This database has been set up for reactions like

X^q+ + Y -> X^(q-1)+(n,l) + Y⁺,

where X = H, H2, He, Be, B, C, N, O, Ne, Ar with charge states q ” 8, and atomic and molecular targets Y = H, He, Li, Be, B, C, N, O, H2, N2, O2, H2O, CO, NO, CO2, CH4 and C2H2. The considered impact energy range is below 10 keV/amu. The regarded papers for experimental and theoretical data were published in the period 1989 to June 2000. The used program is named „FileMaker Pro“ and the files are called „h_he_cap.data“ for H- and He projectiles, „be_ne_cap.data“ for Be-, B-, C-, N-, O- and Ne projectiles and „ar_cap.data“

for Ar projectiles. The files contain the following information about the reaction partners:

Charge states of the projectiles and the atomic and molecular targets, the kind of work

sections, electron capture rate coefficients, translation energy spectra etc.). The experimental setups and the theoretical treatments are shortly described, and the first author and the name of the publishing journal are listed as well.

We have retrieved 232 relevant papers, 131 for the experimental and 146 for the theoretical data. File h_he_cap.data contains in total 130 papers: 96 with data for electron capture cross sections and 34 with other kind of data like TE spectra (11 papers), rate coefficients for electron capture (5 papers), alignment parameters (2 papers), excitation and ionization cross sections (17 papers). File be_ne_cap.data contains 102 papers: 87 for electron capture cross sections and 16 for TE spectra, and ar_cap.data contains 20 for electron capture cross sections and 4 for other kind of data.

For projectiles in specific charge states q we have found a number of experimental and theoretical papers as indicated in the following table.

H

The full version of our database can be downloaded from our homepage http://www.iap.tuwien.ac.at/www/atomic/cxdatabase

Databases for Atomic and Molecular Physics accessible on the Internet

Most useful databases for electron capture processes in the low energy range are ORNL - Controlled Fusion Atomic Data Center, http://www-cfadc.phys.ornl.gov, and

NIFS - Atomic Databases-Data Planing Center, National Institute for Fusion Science, Japan, http://amdata.nifs.ac.jp

For experimental and theoretical electron capture cross sections for H-, H2- and He- like projectiles on H, He, Ne, Ar, Kr, Xe, H2, N2, O2, H2O, C, CH4, C2H4, C2H6, C4H10, CO, CO2

we have found the following database especially useful:

JEAMDL - Japanese Evaluated Atomic and Molecular Data, Library - JAERY (Japan Atomic Energy Research Institute), http://wwwndc.tokai.jaeri.go.jp/JEAMDL/images/.

This database covers a large energy range (1 - 10⁸ eV) for the period from 1950 until present.

All cross sections contained are plotted and interpolated.

Further useful databases for Atomic and Molecular Physics are listed below.

NIST - Physical Reference Data, http://physics.nist.gov/PhysRefData/contents.htm e + H, He, H2, N2, O2, CO, CO2, NO, NH3, CnHm (n = 1 - 6, m = 1 - 8)

AMDIS (Atomic and Molecular Data Information System) Bibliographic Database (AMBDAS), http://www-amdis.iaea.org/: H, He, B, Be, Ne, C, N, O + H, He, Li, Na, Be, B, C, N, O, H2, N2, O2, CO, CO2, NO, CH4, C2H2.

AMODS (Atomic, Molecular and Optical Database System) Library - KAERY (Korea Atomic Energy Research Institute), http://amods.kaeri.re.kr/:

e + H, He, O, H2, N2, O2, H2O, CO2, SO2, CH4

GAPHYOR - Data Center, http://gaphyor.lpqp.u-psud.fr/: H, He, B, Be, Ne, C, N, O + H, He, Li, Na, Be, B, C, N, O, H2, N2, O2, CO, CO2, NO, CH4, C2H2.

WEIZMANN - Databases for Atomic and Plasma Physics http://plasma-gate.weizmann.ac.il/DBfaPP.html

EDP Sciences, http://www.ed-phys.fr/docinfos/journals.html

Institute of Physics - INSPEC Database from the IEE, http://www.iop.org/JR/.

ACKNOWLEDGEMENT

This work has been conducted within Association EURATOM-OEAW, with measurements described in chapter 2 supported by Austrian FWF.

REFERENCES

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[2] P. Leputsch, Thesis, TU Wien (1998, unpublished) [3] HP. Winter, J. Phys. Chem. 99(1995)15448

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[6] S. Bashkin and J.O. Stoner, jr., Atomic Energy Levels and Grotrian Diagrams I, North Holland, Amsterdam 1975

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