Electron-ion recombination rate coefficient measurements in a flowing afterglow plasma

“…This ion was first detected in space and then synthesized in the laboratory [20]. Experimental measurements of DR in HCO + were realized in a number of merged-beam, afterglow-plasma, and storage ring experiments [21,22,23,24,25,26,27,28,29,30]. In Ref.…”

Section: Introductionmentioning

confidence: 99%

Renner-Teller effects inHCO+dissociative recombination

et al. 2006

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“…12,20,34,60 In the research presented here we have managed to control and reproduce a number of significantly different vibrational populations. We were able to smoothly vary the ion population from vibrationally cool to vibrationally hot.…”

Section: Discussionmentioning

confidence: 99%

“…The reported laboratory values [3][4][5][6][7][8][9][10][11][12][13] range from 1.7•10 Ϫ7 to 2.4•10 Ϫ7 cm 3 s Ϫ1 at 300 K. The commonly used value for ground-state oxygen ions at 300 K is 1.95•10 Ϫ7 cm 3 s Ϫ1 . In general, the temperature dependence of the thermal rate coefficient is reported to follow ␣(O 2 ϩ )ϳT Ϫ0.7 with T pertaining mainly to the electron temperature.…”

Section: Introductionmentioning

confidence: 99%

Vibrationally resolved rate coefficients and branching fractions in the dissociative recombination of O2+

Petrignani

Zande

Cosby

et al. 2004

The Journal of Chemical Physics

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We have studied the dissociative recombination of the first three vibrational levels of O 2 ϩ in its electronic ground X 2 ⌸ g state. Absolute rate coefficients, cross sections, quantum yields and branching fractions have been determined in a merged-beam experiment in the heavy-ion storage ring, CRYRING, employing fragment imaging for the reaction dynamics. We present the absolute total rate coefficients as function of collision energies up to 0.4 eV for five different vibrational populations of the ion beam, as well as the partial ͑vibrationally resolved͒ rate coefficients and the branching fractions near 0 eV collision energy for the vibrational levels vϭ0, 1, and 2. The vibrational populations used were produced in a modified electron impact ion source, which has been calibrated using Cs-O 2 ϩ dissociative charge transfer reactions. The measurements indicate that at low collision energies, the total rate coefficient is weakly dependent on the vibrational excitation. The calculated thermal rate coefficient at 300 K decreases upon vibrational excitation. The partial rate coefficients as well as the partial branching fractions are found to be strongly dependent on the vibrational level. The partial rate coefficient is the fastest for vϭ0 and goes down by a factor of two or more for vϭ1 and 2. The O( 1 S) quantum yield, linked to the green airglow, increases strongly upon increasing vibrational level. The effects of the dissociative recombination reactions and super elastic collisions on the vibrational populations are discussed.

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“…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.…”

Section: Introductionmentioning

confidence: 96%

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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Electron-ion recombination rate coefficient measurements in a flowing afterglow plasma

Cited by 62 publications

References 27 publications

Renner-Teller effects inHCO+dissociative recombination

Renner-Teller effects inHCO+dissociative recombination

Vibrationally resolved rate coefficients and branching fractions in the dissociative recombination of O2+

A critical review of H₃⁺recombination studies

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Electron-ion recombination rate coefficient measurements in a flowing afterglow plasma

Cited by 62 publications

References 27 publications

Renner-Teller effects inHCO+dissociative recombination

Renner-Teller effects inHCO+dissociative recombination

Vibrationally resolved rate coefficients and branching fractions in the dissociative recombination of O2+

A critical review of H3+recombination studies

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A critical review of H₃⁺recombination studies