Reactions of H2 with He+ at temperatures below 40 K

Schauer, Martin; Jefferts, Steven R.; Barlow, Stephan E.; Dunn, G. H.

doi:10.1063/1.456748

Cited by 41 publications

(18 citation statements)

References 20 publications

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“…For RCT, the calculated rates show a monotonically decreasing trend with respect to increasing temperature. The shape and magnitude of the calculated rate constant are in reasonably good agreement with the measurements of Schauer et al [11] and the upper-limit values of Johnsen, Chen, and Biondi [8], and are similar in nature to the results previously obtained for the He +H system [12]. In addition, as was found for low-energy ion-atom collisions, the present RCT cross section shows pronounced "predissociation" resonance peaks (not shown) at several characteristic energies, corresponding to transient vibrational and rotational states of the [HeHz]+ complex that are temporarily bound by the centrifugal barrier in the effective potential.…”

Section: B Dissociative Charge Transfersupporting

confidence: 86%

“…4 and 5 for RCT and DCT, respectively, along with the measurements by Schauer et r/I. [11] and others. For RCT, the calculated rates show a monotonically decreasing trend with respect to increasing temperature.…”

Section: B Dissociative Charge Transfersupporting

confidence: 54%

“…The experimental findings of Schauer et al [11] sug-gest that these exoergic inelastic processes are slow compared to most other ion-molecule reactions, the measured rate constants being 3.0X10 ' cm /s for DCT and 1.0X10 ' cm /s for RCT at 15 K. Their results also call into question earlier experimental results obtained at somewhat higher temperatures by different groups [8 -10]. Earlier studies [2 -6] of the adiabatic potential-energy surfaces suggested the presence of an avoided crossing that would constitute a potential barrier between the initial and the final channels for DCT.…”

Section: Introductionmentioning

confidence: 93%

“…Unfortunately, rigorous, systematic studies of the collision dynamics of this system are scarce for any regime of collision energies, in contrast to the plentiful quantumchemical calculations of the molecular potential surfaces [3 -7]. Several experimental measurements have determined reaction rates for various exoergic inelastic processes in He +H2 collisions under conditions that simulate the astrophysical environment [8 -10], and Schauer et al [11] recently measured absolute rate constants at ultralow energy in an experiment using a Penning ion trap. Specifically, the reaction rates measured are (i) dissociative charge transfer (DCT)…”

Section: Introductionmentioning

confidence: 99%

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Theoretical study of charge transfer inHe++H2collisions in the

Kimura

Lane

1991

Phys. Rev. A

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A theoretical investigation of charge transfer in He +H2 collisions in the ultralow-energy regime (meV) has been conducted. Molecular states have been obtained by using the multiconfiguration selfconsistent-field method. The reaction rate constants have been calculated for dissociative and radiative charge-transfer processes. Agreement with the recent measurements of Schauer et al. [J. Chem. Phys. 91, 4593 (1989)] is satisfactory. The present study provides a theoretical rationale for the experimental findings by interpreting the detailed collision dynamics.

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Section: B Dissociative Charge Transfersupporting

confidence: 86%

Section: B Dissociative Charge Transfersupporting

confidence: 54%

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Theoretical study of charge transfer inHe++H2collisions in the

Kimura

Lane

1991

Phys. Rev. A

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“…As CO depletes on to grains, there is competition with reaction (16) (Schauer et al 1989). Thus, the rate of production of carbon ions is ζ He n(He)f C , where ζ He = 0.5ζ H 2 is the rate of cosmic ray ionization of He and…”

Section: Simplified Analysis Of the Chemistrymentioning

confidence: 99%

Nitrogen chemistry and depletion in starless cores

Hily-Blant¹,

Walmsley

Forêts

et al. 2010

A&A

119

128

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Aims. We investigated the chemistry of nitrogen-containing species, principally isotopologues of CN, HCN, and HNC, in a sample of pre-protostellar cores. Methods. We used the IRAM 30 m telescope to measure the emission in rotational and hyperfine transitions of CN, HCN, 13 CN, H 13 CN, HN 13 C, and HC 15 N in L 1544, L 183, Oph D, L 1517B, L 310. The observations were made along axial cuts through the dust emission peak, at a number of regularly-spaced offset positions. The observations were reduced and analyzed to obtain the column densities, using the measurements of the less abundant isotopic variants in order to minimize the consequences of finite optical depths in the lines. The observations were compared with the predictions of a free-fall gravitational collapse model, which incorporates a non-equilibrium treatment of the relevant chemistry. Results. We found that CN, HCN, and HNC remain present in the gas phase at densities well above that at which CO depletes on to grains. The CN:HCN and the HNC:HCN abundance ratios are larger than unity in all the objects of our sample. Furthermore, there is no observational evidence for large variations of these ratios with increasing offset from the dust emission peak and hence with density. Whilst the differential freeze-out of CN and CO can be understood in terms of the current chemistry, the behaviour of the CN:HCN ratio is more difficult to explain. Models suggest that most nitrogen is not in the gas phase but may be locked in ices. Unambiguous conclusions require measurements of the rate coefficients of the key neutral-neutral reactions at low temperatures.

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Applications of the Jupiter Global Ionosphere‐Thermosphere Model: A case study of auroral electron energy deposition

2017

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We investigate auroral energy deposition by using a nonhydrostatic global atmospheric model coupled to a two‐stream electron transport model. We present several electron beam study cases, discussing energy flux and electron energy effects on the ion and neutral densities, the atmospheric thermal profile, H3+ and hydrocarbon infrared (IR) emissions, H2 far ultraviolet (FUV) emissions and color ratios, and vibrationally excited molecular hydrogen. Using the nonhydrostatic Jupiter Global Ionosphere‐Thermosphere Model, we find that FUV spectral characteristics consistent with previous Hubble Space Telescope results derive primarily from electrons with energies above 10 keV, over energy fluxes of 10–100 erg/cm2 s, while IR emissions are predominantly due to electrons with energies below 10 keV, over energy fluxes of 10–100 erg/cm2 s. Electrons with energies below about 10 keV produce enough H2(ν) to deplete the H+ population, modifying the ionospheric composition, and consequently the H3+ emissions, which can be used to directly relate H2 vibrational excitation to auroral observations. New observations by Juno will provide better electron energy distributions to constrain the electron energy spectrum and magnitude at the upper boundary of the model and simultaneously provide a determination of the FUV and IR spectra that can be cross‐correlated with the observations.

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Reactions of H2 with He+ at temperatures below 40 K

Cited by 41 publications

References 20 publications

Theoretical study of charge transfer inHe++H2collisions in the

Theoretical study of charge transfer inHe++H2collisions in the

Nitrogen chemistry and depletion in starless cores

Applications of the Jupiter Global Ionosphere‐Thermosphere Model: A case study of auroral electron energy deposition

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