Measurements of Recombination of Electrons with<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow /><mml:mrow /><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></

Leu, Ming‐Taun; Biondi, Manfred A.; Johnsen, Rainer

doi:10.1103/physreva.8.413

Cited by 138 publications

(37 citation statements)

References 21 publications

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“…The earliest afterglow measurements in which the recombining ions were identified by mass analysis are those of Leu et al (1973) [7] and by Macdonald et al (1984) [8] [31], based on their calculations of two-dimensional potential-energy curves, predicted that the ionic ground-potential curve of H 3 + does not be intersect a repulsive curve leading to neutral products. Actually, a similar prediction had been made earlier by Kulander and Guest [32].…”

Section: Early Stationary Afterglow Resultsmentioning

confidence: 99%

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: Early Stationary Afterglow Resultsmentioning

confidence: 99%

A critical review of H₃⁺recombination studies

Johnsen¹

2005

J. Phys.: Conf. Ser.

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“…The apparent absence of such effects, however, does not rule out that they made a contribution. As a case in point, consider one of the earliest measurements, the microwave afterglow experiment of Leu et al [4] The authors obtained a consistent 300 K rate coefficient of 2.4 × 10 −7 cm 3 /s that did not vary when the neutral helium density was changed from 4 × 10 17 cm −3 to twice that value. Neither did they observe a dependence on electron density in the range from 5 × 10 9 cm −3 to less than one tenth of that value.…”

Section: Experimental Data On Third-body Effectsmentioning

confidence: 99%

“…Comparison of the model to experimental data at T = 300 K. Fitting parameters: cap = 2.6 × 10 −7 cm 3 /s, k H e = 2 × 10 −9 cm 3 /s, k e = 1 × 10 −1 cm 3 /s, ν diss, 0 = 1 × 10 8 1/s, ν a = 8 × 10 8 1 /s. Data: Gougousi et al [7], Smith and Spanel [6], CRDS and Cryo-FALP I from Glosík et al [3], and Leu et al [4].…”

Section: Tentative Model Of 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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“…Afterglow plasmas at higher densities, however, explore additional mechanisms to return to the neutral state, as is immediately apparent when one examines historical recombination data. Figure 1 compares selected afterglow rate coefficients [2,3,5,6] to the thermal recombination coefficient inferred from earlier ISR experiments [4].…”

Section: Introductionmentioning

confidence: 99%

“…This brief contribution adds some ideas on the interpretation of afterglow data, and proposed three-body 10 -6 Macdonald et al [2] Glosík et al [3] McCall et al [4] Amano [5] Leu et al [6] 10 -7…”

Section: Introductionmentioning

confidence: 99%

Kinetic processes in recombining H ₃ ⁺ plasmas

Johnsen

2012

Phil. Trans. R. Soc. A.

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Measurements of Recombination of Electrons withH3+andH

Cited by 138 publications

References 21 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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Measurements of Recombination of Electrons withH3+andH

Cited by 138 publications

References 21 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