Rainer Johnsen

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We have studied the dependence of several ion-ion mutual neutralization (MN) reactions on helium density in the range from 1.6 × 10(16) to 1.5 × 10(17) cm(-3) at 300 K, using the Variable Electron and Neutral Density Attachment Mass Spectrometry method. The rate coefficients of the reactions Ar(+) + Br2(-), Ar(+) + SF6(-), and Ar(+) + C7F14(-) were found to(More)
Measurements in H(3)(+) afterglow plasmas with spectroscopically determined relative abundances of H(3)(+) ions in the para-nuclear and ortho-nuclear spin states provide clear evidence that at low temperatures (77-200 K) para-H(3)(+) ions recombine significantly faster with electrons than ions in the ortho state, in agreement with a recent theoretical(More)
Results of an experimental study of binary recombination of para- and ortho-H(3)(+) ions with electrons are presented. Near-infrared cavity-ring-down absorption spectroscopy was used to probe the lowest rotational states of H(3)(+) ions in the temperature range of 77-200 K in an H(3)(+)-dominated afterglow plasma. By changing the para/ortho abundance ratio,(More)
We report thermal rate coefficients for 12 reactions of rare gas cations (Ne(+), Ar(+), Kr(+), Xe(+)) with halide anions (Cl(-), Br(-), I(-)), comprising both mutual neutralization (MN) and transfer ionization. No rate coefficients have been previously reported for these reactions; however, the development of the Variable Electron and Neutral Density(More)
We present experimental evidence that reactions of argon cations Ar(+) with the halogen anions Br(-) and I(-) do not occur exclusively by mutual neutralization, but also produce the cations Br(+) or I(+) ions by transfer ionization (TI). The experiments were carried out in flowing-afterglow plasmas at gas temperatures between and 300 and 500 K, and employed(More)
This paper demonstrates that the transport coefficients of (4)He(+) in (4)He can be calculated over wide ranges of E/N, the ratio of the electrostatic field strength to the gas number density, with the same level of precision as can be obtained experimentally if sufficiently accurate potential energy curves are available for the X(2)Σu (+) and A(2)Σg (+)(More)
The authors have studied CN(B-X) and CN(A-X) emissions produced by the dissociative recombination of HNC+ ions with thermal electrons in a flowing afterglow experiment. A separate drift tube study showed that the reaction Ar(+)+HCN, the precursor reaction used in the flow-tube experiment, produces predominantly HNC+ rather than the more energetic HCN+(More)
We present results of plasma afterglow experiments on ternary electron-ion recombination rate coefficients of H3(+) and D3(+) ions at temperatures from 50 to 300 K and compare them to possible three-body reaction mechanisms. Resonant electron capture into H3* Rydberg states is likely to be the first step in the ternary recombination, rather than(More)
High-level ab initio potential energy curves are calculated for the lowest few states of the [He-Ne](+) complex. RCCSD(T) calculations are employed with large basis sets (up to sextuple-zeta), including extrapolation to the basis set limit, taking account of spin-orbit coupling. In addition, core-valence correlation and multireference effects are(More)
Recombination in plasmas containing H(3)(+) ions occurs not only by binary recombination but also by third-body-assisted mechanisms, the principal subject of this contribution. Third-body effects on recombination are of interest for model calculations of hydrogen discharges, their spectral emissions and the inference of binary recombination coefficients(More)