Recombination of H3+ and D3+ ions in a flowing afterglow plasma

Gougousi, Theodosia; Johnsen, Rainer; Golde, Michael F.

doi:10.1016/0168-1176(95)04248-j

Cited by 64 publications

(77 citation statements)

References 49 publications

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“…The second study, performed after a modification of their flow tube, resulted in a factor-of-two lower value of 7.8 × 10 -8 cm 3 /s at 300 K. Laube et al [17] did not find any variation of the apparent recombination as a function of afterglow time. In contrast, Gougousi et al [16] saw a decline of the recombination rate at late times and found that the apparent recombination rate (inferred from the early afterglow decay) increased from 1. . Gougousi et al attempted to explain their data in terms of a mixture of two different H 3 + vibrational states, but eventually preferred the explanation that the H 3 + recombination proceeded by a three-body mechanism in which both electrons and neutral hydrogen play a role.…”

Section: Afterglow Data After 1984mentioning

confidence: 95%

A critical review of H₃⁺recombination studies

Johnsen¹

2005

J. Phys.: Conf. Ser.

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After more that 30 years of experimental and theoretical work it now appears that theory and experiment on H 3 + recombination have finally converged. Since the storage ring results come very close to the latest theoretical calculations one might conclude that "the case is closed". However, some troublesome issues remain and should not be dismissed too quickly. For instance, some afterglow measurements showed faster decays at early afterglow times. It is now clear that the fast recombining species cannot be vibrationally excited ions since the same rates were found for spectroscopically identified H 3 + ions in v=0. On the other hand, there is no convincing explanation for the very small rates obtained in the Prague experiments at low H 2 densities. It is also puzzling that some measurements find nearly the same recombination coefficients for H 3 + and D 3 + , while others indicate that H 3 + recombines much faster. It has often been stated that vibrational excitation of the H 3 + ions tends to enhance recombination, but the evidence for that is far from solid; some observations suggest that the opposite is just as likely. IntroductionThe history of recombination studies of the H 3 + ion still presents a confusing picture, even to someone who has worked on experimental studies of this ion for more than 30 years and has closely followed the "ups and downs" of experimental results and the interplay between experiment and theory. It is most gratifying that we are now at the point where the best available theory [1, 2] agrees rather well with the latest results of ion-storage-ring experiments [3]. Has the time come to close the books and to say that no further work is needed? I do not think so.If one looks at the experimental results that were obtained over the years (see table 1 and table 2), one notices that the published thermal rate coefficients at temperatures near 300 K have varied by more than one order of magnitude. What shall we make of this large variation? Discarding the older data as "flawed" is not acceptable and may deprive us of useful insights. The variations do not seem to due to ordinary experimental errors such as calibration errors of probes etc. Almost all experimenters also studied the "benchmark ion" O 2 + to test their procedures and in that case the 300 K rate coefficients agree rather well (see e.g. the references to O 2 + data in [4] and [5]). It is far more likely that the poorly controlled and usually unknown internal energy of the H 3 + ion (vibrational, rotational) had an effect on the measured recombination rate. Of course, the vibrational energy of the "benchmark" O 2 + ions also was generally poorly controlled, but fortunately it seems to have only a small effect on the total recombination rate [6] and hence did not lead to significant discrepancies between results.

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Section: Afterglow Data After 1984mentioning

confidence: 95%

A critical review of H₃⁺recombination studies

Johnsen¹

2005

J. Phys.: Conf. Ser.

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“…In the afterglow experiments of Spanel and Smith [6] and of Gougousi et al [7] it was found that the recombination rate slowed down in the late afterglow when the electron density is low. This effect may be due to a ternary reaction with electrons but alternate explanation exist (vibrationally excited ions) that complicate matters.…”

Section: Experimental Data On Third-body Effectsmentioning

confidence: 99%

Three-body mechanisms in plasma recombination of H₃⁺and D₃⁺Ions

Johnsen

2015

EPJ Web of Conferences

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Abstract. The low-temperature plasma recombination of H + 3 and D + 3 ions with electrons partially occurs by three-body assisted (ternary) mechanisms that need to be better understood. Intermediate high Rydberg states are expected to play an important role, but it remains unclear which of their interactions with ambient neutrals and electrons enhance their decay into neutral products. This contribution discusses several proposed models, collisional radiative, collisional dissociative recombination, resonant electron capture, and angular momentum l-mixing. It appears that none of them provides a satisfactory explanation. There is one observation that points to a possibly efficient route to longlived collision complexes that may play a role: Several of the so far unassigned peaks in storage ring data occur at energies where rotational resonances have long lifetimes. A tentative model, based on complex formation and collisional stabilization, leads to qualitative agreement with experiments.

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“…p-electrons, with 'penetrating orbits') interact more efficiently with the ion core and can induce rapid predissociation of the molecular core, thereby completing recombination. The effect of l-mixing due to electrons on H + 3 recombination was first considered by Gougousi et al [18]. Here, we focus on proposed models in which helium atoms are the l-mixing agent.…”

Section: (A) Collisional Radiative Recombination and Collisional Dissmentioning

confidence: 99%

“…Most available data indicate that the electron density (in the experimental range) has little effect. An element of doubt remains, however (see [18]). …”

Section: Afterglows In Rare-gas/h 2 Mixturesmentioning

confidence: 99%

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Kinetic processes in recombining H ₃ ⁺ plasmas

Johnsen

2012

Phil. Trans. R. Soc. A.

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Recombination of H3+ and D3+ ions in a flowing afterglow plasma

Abstract: Abstract

Cited by 64 publications

References 49 publications

A critical review of H₃⁺recombination studies

A critical review of H₃⁺recombination studies

Three-body mechanisms in plasma recombination of H₃⁺and D₃⁺Ions

Kinetic processes in recombining H ₃ ⁺ plasmas

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Recombination of H3+ and D3+ ions in a flowing afterglow plasma

Abstract: Abstract

Cited by 64 publications

References 49 publications

A critical review of H3+recombination studies

A critical review of H3+recombination studies

Three-body mechanisms in plasma recombination of H3+and D3+Ions

Kinetic processes in recombining H 3 + plasmas

Contact Info

Product

Resources

About

A critical review of H₃⁺recombination studies

A critical review of H₃⁺recombination studies

Three-body mechanisms in plasma recombination of H₃⁺and D₃⁺Ions

Kinetic processes in recombining H ₃ ⁺ plasmas