LOW-TEMPERATURE ION TRAP STUDIES OF N+(3Pja) + H2(j) → NH++ H

Zymak, Illia; Hejduk, Michal; Mulin, Dmytro; Plašil, R.; Glosı́k, J.; Gerlich, D.

doi:10.1088/0004-637x/768/1/86

Cited by 41 publications

(64 citation statements)

References 15 publications

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“…The reverse reaction rate coefficient, k r , is obtained by Marquette et al (1988) Marquette et al (1988) and o-H 2 . Similar results were obtained by Zymak et al (2013), who also emphasized the possible role of the fine structure level of 14 N + . We follow the prescription derived by Dislaire et al (2012) and extend their analysis to deuterated forms and those including 15 N, as displayed in Table 2.…”

Section: Ammonia Synthesissupporting

confidence: 87%

Isotopic fractionation of carbon, deuterium, and nitrogen: a full chemical study

Roueff

Loison

Hickson

2015

A&A

171

349

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Context. The increased sensitivity and high spectral resolution of millimeter telescopes allow the detection of an increasing number of isotopically substituted molecules in the interstellar medium. The 14 N/ 15 N ratio is difficult to measure directly for molecules containing carbon. Aims. Using a time-dependent gas-phase chemical model, we check the underlying hypothesis that the 13 C/ 12 C ratio of nitriles and isonitriles is equal to the elemental value. Methods. We built a chemical network that contains D, 13 C, and 15 N molecular species after a careful check of the possible fractionation reactions at work in the gas phase. Results. Model results obtained for two different physical conditions that correspond to a moderately dense cloud in an early evolutionary stage and a dense, depleted prestellar core tend to show that ammonia and its singly deuterated form are somewhat enriched in 15 N, which agrees with observations. The 14 N/ 15 N ratio in N 2 H + is found to be close to the elemental value, in contrast to previous models that obtain a significant enrichment, because we found that the fractionation reaction between 15 N and N 2 H + has a barrier in the entrance channel. The high values of the N 2 H + / 15 NNH + and N 2 H + /N 15 NH + ratios derived in L1544 cannot be reproduced in our model. Finally, we find that nitriles and isonitriles are in fact significantly depleted in 13 C, thereby challenging previous interpretations of observed C 15 N, HC 15 N, and H 15 NC abundances from 13 C containing isotopologues.

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Section: Ammonia Synthesissupporting

confidence: 87%

Isotopic fractionation of carbon, deuterium, and nitrogen: a full chemical study

Roueff

Loison

Hickson

2015

A&A

171

349

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“…Moreover, at low temperatures, H 2 molecules also act as a buffer gas because of the low probability for a reactive collision. Recent experiments in our apparatus (Zymak et al 2013;Plašil et al 2012) as well as in other 22-pole trap experiments have confirmed that the collisional temperature is slightly higher than the temperature of the trap. In the present case we can safely assume that the collisional temperature in interaction of OD − with H 2 does not exceed the trap temperature by more than 10 K. For simplicity of presentation, we define the collisional temperature as T = T 22PT + 5 K with an uncertainty of ± 5 K.…”

Section: Methodssupporting

confidence: 76%

Effect of rotational excitation of H₂ on isotopic exchange reaction with OD⁻ at low temperatures

Roučka

Rednyk

Kovalenko

et al. 2018

A&A

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Aims. This paper presents experimentally obtained rate coefficients for the weakly endothermic reaction OD − + H 2 → OH − + HD with ortho-and para-hydrogen at astrophysically relevant temperatures between 10 and 300 K. Methods. The reaction was studied with normal and para-enriched (99.5% para-H 2 ) hydrogen in a 22-pole ion trap. The measured temperature dependencies of reaction rate coefficients are analyzed using a model which assumes that the rotational energies of the two reactants are equivalent to the translational energy in driving the reaction. Results. At room temperature, the rate coefficients of reactions with both nuclear spin variants reach 7 × 10 −11 cm 3 s −1 , which is in good agreement with the previous results from ion trap and swarm experiments with normal hydrogen. Cooling down the trap slows down the reaction and leads, at a nominal trap temperature of 11 K, to a rate coefficient below 10 −14 cm 3 s −1 for paraenriched hydrogen. The fitted reaction endothermicity of 25.3 ± 2.2 meV agrees well with the literature value calculated in the Born-Oppenheimer approximation, ∆H 0 = 24.0 meV. A simpler evaluation procedure, fitting the data with Arrhenius functions, results in p k = 16.8 × 10 −11 exp(−234 K/T ) cm 3 s −1 for pure para-hydrogen and o k = 9.4 × 10 −11 exp(−101 K/T ) cm 3 s −1 for pure orthohydrogen.

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“…The Nautilus code computes the temporal evolution of the gas-phase and ice mantle composition considering the reaction network kida.uva.2014 (http://kida.obs.u-bordeaux1.fr/models, (Wakelam et al 2015)), the grainsurface reactions being similar to Garrod et al (2007 Marquette et al (1988), reflecting the endothermic nature of the N + + p-H 2 reaction. In the second case (case II), to simulate an OPR = 3 (the statistical ratio considering the large exothermicity of H 2 production on grain surfaces (Gavilan et al 2012;Naoki et al 2010)) we use a rate constant for reaction (1) k N+ + H2 (10 K) = 2.9 ⋅ 10 -11 cm 3 molecule -1 s -1 , based on the recent measurements by (Zymak et al (2013).…”

Section: Astrochemical Modelmentioning

confidence: 99%

“…N 2 itself is produced by atomic nitrogen reactions with small neutral radicals (Daranlot et al 2012;Le Gal et al 2014) which experimental and theoretical studies have shown to be less efficient than previously assumed (Daranlot et al 2012;Daranlot et al 2013;Daranlot et al 2011;Jorfi & Honvault 2009;Loison et al 2014a;Ma et al 2012 (Vigren et al 2012) which is nonetheless sufficient to make this process the major source of NH radicals in current gas-phase astrochemical models (Le Gal et al 2014). Reaction (R1) is problematic due to the endothermicity of the N + + para-H 2 (p-H 2 ) reaction (Zymak et al 2013). In the current state of modeling studies, N + reacts with ortho-H 2 (o-H 2 ) many orders of magnitude faster than with p-H 2 at temperatures relevant to dense interstellar clouds.…”

Section: Introductionmentioning

confidence: 99%

THE C(³P) + NH₃REACTION IN INTERSTELLAR CHEMISTRY. II. LOW TEMPERATURE RATE CONSTANTS AND MODELING OF NH, NH₂, AND NH₃ABUNDANCES IN DENSE INTERSTELLAR CLOUDS

Hickson

Loison

Bourgalais

et al. 2015

ApJ

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A continuous supersonic flow reactor has been used to measure rate constants for the C( 3 P) + NH 3 reaction over the temperature range 50-296 K. C( 3 P) atoms were created by the pulsed laser photolysis of CBr 4 . The kinetics of the title reaction were followed directly by vacuum ultraviolet laser induced fluorescence (VUV LIF) of C( 3 P) loss and through H( 2 S) formation. The experiments show unambiguously that the reaction is rapid at 296 K, becoming faster at lower temperatures, reaching a value of (1.8 ± 0.2) ⋅ 10 -10 cm 3 molecule -1 s -1 at 50 K. As this reaction is not currently included in astrochemical networks, its influence on interstellar nitrogen hydride abundances is tested through a dense cloud model including gas-grain interactions. In particular, the effect of the ortho-to-para ratio of H 2 which plays a crucial role in interstellar NH 3 synthesis is examined.

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LOW-TEMPERATURE ION TRAP STUDIES OF N⁺(³P_ja) + H₂(j) → NH⁺+ H

Cited by 41 publications

References 15 publications

Isotopic fractionation of carbon, deuterium, and nitrogen: a full chemical study

Isotopic fractionation of carbon, deuterium, and nitrogen: a full chemical study

Effect of rotational excitation of H₂ on isotopic exchange reaction with OD⁻ at low temperatures

THE C(³P) + NH₃REACTION IN INTERSTELLAR CHEMISTRY. II. LOW TEMPERATURE RATE CONSTANTS AND MODELING OF NH, NH₂, AND NH₃ABUNDANCES IN DENSE INTERSTELLAR CLOUDS

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LOW-TEMPERATURE ION TRAP STUDIES OF N+(3Pja) + H2(j) → NH++ H

Cited by 41 publications

References 15 publications

Isotopic fractionation of carbon, deuterium, and nitrogen: a full chemical study

Isotopic fractionation of carbon, deuterium, and nitrogen: a full chemical study

Effect of rotational excitation of H2 on isotopic exchange reaction with OD− at low temperatures

THE C(3P) + NH3REACTION IN INTERSTELLAR CHEMISTRY. II. LOW TEMPERATURE RATE CONSTANTS AND MODELING OF NH, NH2, AND NH3ABUNDANCES IN DENSE INTERSTELLAR CLOUDS

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LOW-TEMPERATURE ION TRAP STUDIES OF N⁺(³P_ja) + H₂(j) → NH⁺+ H

Effect of rotational excitation of H₂ on isotopic exchange reaction with OD⁻ at low temperatures

THE C(³P) + NH₃REACTION IN INTERSTELLAR CHEMISTRY. II. LOW TEMPERATURE RATE CONSTANTS AND MODELING OF NH, NH₂, AND NH₃ABUNDANCES IN DENSE INTERSTELLAR CLOUDS