Complex formation in electron-ion recombination of molecular ions

Johnsen, Rainer; Mitchell, James B.

doi:10.1016/s1071-9687(98)80004-x

Cited by 8 publications

(4 citation statements)

References 73 publications

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“…X 2 Q i ) emissions from the electron-ion recombination of H 2 O þ in a crossed beam experiment (Sonnenfroh et al, 1993). More recently, the flowing afterglow has been used to great effect (see the reviews, Adams, 1992Adams, , 1993Adams, , 1994Johnsen and Mitchell, 1998;Johnsen et al, 2000;Tsuji, 2001). All of these data are compiled in Table 4 with the earlier data being included for completeness; the same basic technique was used in all of the studies.…”

Section: Internal Excitation Of Recombination Productsmentioning

confidence: 99%

Electron molecular ion recombination: Product excitation and fragmentation

Adams

Poterya

Babcock

2006

Mass Spectrometry Reviews

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Electron-ion dissociative recombination is an important ionization loss process in any ionized gas containing molecular ions. This includes the interstellar medium, circumstellar shells, cometary comae, planetary ionospheres, fusion plasma boundaries, combustion flames, laser plasmas and chemical deposition and etching plasmas. In addition to controlling the ionization density, the process generates many radical species, which can contribute to a parallel neutral chemistry. Techniques used to obtain rate data and product information (flowing afterglows and storage rings) are discussed and recent data are reviewed including diatomic to polyatomic ions and cluster ions. The data are divided into rate coefficients and cross sections, including their temperature/energy dependencies, and quantitative identification of neutral reaction products. The latter involve both ground and electronically excited states and including vibrational excitation. The data from the different techniques are compared and trends in the data are examined. The reactions are considered in terms of the basic mechanisms (direct and indirect processes including tunneling) and recent theoretical developments are discussed. Finally, new techniques are mentioned (for product identification; electrostatic storage rings, including single and double rings; Coulomb explosion) and new ways forward are suggested.

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Section: Internal Excitation Of Recombination Productsmentioning

confidence: 99%

Electron molecular ion recombination: Product excitation and fragmentation

Adams

Poterya

Babcock

2006

Mass Spectrometry Reviews

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“…H 3 Rydberg molecules would be the prime candidates for reionization, and as such, they could have easily been missed in high-field experiments. Based on these data, Mitchell and Johnsen suggested that H 3 Rydberg molecules could have accounted for as much as 80% of the DR products …”

Section: H3 Rydberg Moleculesmentioning

confidence: 99%

“…Based on these data, Mitchell and Johnsen suggested that H 3 Rydberg molecules could have accounted for as much as 80% of the DR products. 21 In 2006, Glosi ́k continued a series of promising afterglow experiments in Prague using cavity ringdown spectroscopy to record spectra of triatomic isotopomers in discharged mixtures of hydrogen and deuterium (H 3 + , H 2 D + , HD 2 + ) originating from low rotational states. 14 In subsequent low-temperature ion trap experiments at MPIK Heidelberg and TU Chemnitz, Glosi ́k recorded near-infrared spectra of H 3 + , H 2 D + , and HD 2 + and characterized the trapped ions at temperatures near 10 K. These low-energy interactions are directly relevant to interstellar conditions, especially in cold dense regions of space where deuterated molecules are abundant.…”

Section: ■ Introductionmentioning

confidence: 99%

Rydberg States of H₃ and HeH as Potential Coolants for Primordial Star Formation

et al. 2021

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Current theory and measurements establish the age of the universe as ca. 13.8 billion years. For the first several hundred million years of its existence, it was a dark, opaque void. After that, the hydrogen atoms comprising most of the "ordinary" matter began to condense and ionize, eventually forming the first stars that would illuminate the sky. Details of how these "primordial" stars formed have been widely debated, but remain elusive. A central issue in this process is the mechanism by which the primordial gas (mainly hydrogen and helium atoms) collected via the action of dark matter cools and further accretes to fusion densities. Current models invoke collisional excitation of H 2 molecular rotations and subsequent radiative rotational transitions allowed by the weak molecular quadrupole moment. In this article, we review the salient considerations, and present some new ideas, bases on recent spectroscopic observations of neutral H 3 Rydberg electronic state emission in the mid-infrared.

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“…The merged-beam experiment may have been subject to other effects. Mitchell (in Mitchell and Johnsen [46]) describes a merged-beam experiment in which the deflection field used to separate product neutrals from the ions in the post-collision region was varied. It was found that the measured DR product signal increased by a factor of five (approaching that obtained in ISR experiments) when the field strength in that region was reduced from 3000 V/cm to 200 V/cm.…”

Section: Single-pass Merged-beam Datamentioning

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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Complex formation in electron-ion recombination of molecular ions

Cited by 8 publications

References 73 publications

Electron molecular ion recombination: Product excitation and fragmentation

Electron molecular ion recombination: Product excitation and fragmentation

Rydberg States of H₃ and HeH as Potential Coolants for Primordial Star Formation

A critical review of H₃⁺recombination studies

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Complex formation in electron-ion recombination of molecular ions

Cited by 8 publications

References 73 publications

Electron molecular ion recombination: Product excitation and fragmentation

Electron molecular ion recombination: Product excitation and fragmentation

Rydberg States of H3 and HeH as Potential Coolants for Primordial Star Formation

A critical review of H3+recombination studies

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Rydberg States of H₃ and HeH as Potential Coolants for Primordial Star Formation

A critical review of H₃⁺recombination studies