Electron-impact rotational excitation of : relevance for thermalization and dissociation dynamics

Electrons are known to be efficient in rotationally exciting molecular ions in low-density astrophysical plasmas. Rotational excitation of molecular ions has also been shown to affect the measured values of dissociative recombination (DR) rate coefficients. Thus, electron collisions with are expected to play a significant role in thermalization and dissociation dynamics of this ion, both in the laboratory and in space. Using the molecular R -matrix method combined with the adiabatic-nuclei-rotation approximation, we have computed new rate coefficients for the rotational excitation of by electrons at temperatures from 10 to 10 000 K. De-excitation rates are found to amount to a few 10 −7 cm 3 s −1 below 1000 K, i.e. comparable in magnitude to that of DR. In astrophysical environments where the electron fraction exceeds 10 −4 , electron collisions are thus expected to contribute to the non-thermal rotational distribution of . The competition between electron and neutral collisions is discussed in the context of recent observations of towards Galactic centre sources.

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Quantum-state–selective electron recombination studies suggest enhanced abundance of primordial HeH+

Science ◽

10.1126/science.aax5921 ◽

2019 ◽

Vol 365 (6454) ◽

pp. 676-679 ◽

Cited By ~ 13

Author(s):

Oldřich Novotný ◽

Patrick Wilhelm ◽

Daniel Paul ◽

Ábel Kálosi ◽

Sunny Saurabh ◽

...

Keyword(s):

Galaxy Formation ◽

Dissociative Recombination ◽

Molecular Ions ◽

Rate Coefficients ◽

Specific Rate ◽

Electron Recombination ◽

Recombination Rates ◽

Rotational States ◽

Hydride Ion ◽

Helium Hydride

The epoch of first star formation in the early Universe was dominated by simple atomic and molecular species consisting mainly of two elements: hydrogen and helium. Gaining insight into this constitutive era requires a thorough understanding of molecular reactivity under primordial conditions. We used a cryogenic ion storage ring combined with a merged electron beam to measure state-specific rate coefficients of dissociative recombination, a process by which electrons destroy molecular ions. We found a pronounced decrease of the electron recombination rates for the lowest rotational states of the helium hydride ion (HeH+), compared with previous measurements at room temperature. The reduced destruction of cold HeH+ translates into an enhanced abundance of this primordial molecule at redshifts of first star and galaxy formation.

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The effect of CO−H2O collisions in the rotational excitation of cometary CO

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa242 ◽

2020 ◽

Vol 493 (1) ◽

pp. 776-782 ◽

Cited By ~ 3

Author(s):

A Faure ◽

F Lique ◽

J Loreau

Keyword(s):

Radiative Decay ◽

Energy Surface ◽

Population Distribution ◽

Rate Coefficients ◽

Intermolecular Potential ◽

Kinetic Temperature ◽

Rotational Excitation ◽

Rotational Distribution ◽

High Level ◽

The Impact

ABSTRACT We present the first accurate rate coefficients for the rotational excitation of CO by H2O in the kinetic temperature range 5–100 K. The statistical adiabatic channel method (SACM) is combined with a high-level rigid-rotor CO−H2O intermolecular potential energy surface. Transitions among the first 11 rotational levels of CO and the first 8 rotational levels of both para-H2O and ortho-H2O are considered. Our rate coefficients are compared to previous data from the literature and they are also incorporated in a simple non-LTE model of cometary coma including collision-induced transitions, solar radiative pumping and radiative decay. We find that the uncertainties in the collision data have significant influence on the CO population distribution for H2O densities in the range 103–108 cm−3. We also show that the rotational distribution of H2O plays an important role in CO excitation (owing to correlated energy transfer in both CO and H2O), while the impact of the ortho-to-para ratio of H2O is found to be negligible.

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Photodestruction of Diatomic Molecular Ions: Laboratory and Astrophysical Application

Molecules ◽

10.3390/molecules26010151 ◽

2020 ◽

Vol 26 (1) ◽

pp. 151

Author(s):

Vladimir A. Srećković ◽

Ljubinko M. Ignjatović ◽

Milan S. Dimitrijević

Keyword(s):

Cross Sections ◽

Alkali Metals ◽

Molecular State ◽

Molecular Ions ◽

Rate Coefficients ◽

Astrophysical Plasmas ◽

Stellar Objects ◽

Laboratory Plasmas ◽

Rovibrational States ◽

The Individual

In this work, the processes of photodissociation of some diatomic molecular ions are investigated. The partial photodissociation cross-sections for the individual rovibrational states of the diatomic molecular ions, which involves alkali metals, as well as corresponding data on molecular species and molecular state characterizations, are calculated. Also, the average cross-section and the corresponding spectral absorption rate coefficients for those small molecules are presented in tabulated form as a function of wavelengths and temperatures. The presented results can be of interest for laboratory plasmas as well as for the research of chemistry of different stellar objects with various astrophysical plasmas.

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Гелиевое послесвечение без метастабильных частиц

Журнал технической физики ◽

10.21883/os.2019.12.48681.156-19 ◽

2019 ◽

Vol 127 (12) ◽

pp. 890

Author(s):

В.А. Иванов ◽

Ю.Э. Скобло

Keyword(s):

Radiative Recombination ◽

Barrier Discharge ◽

Early Stage ◽

Dissociative Recombination ◽

Molecular Ions ◽

Low Density ◽

Atomic Ions ◽

Excited Atoms ◽

Small Admixture ◽

Vibrational Kinetics

The results of a spectroscopic study of the afterglow of a pulsed barrier discharge in helium with a small admixture of neon, which creates a plasma with a low density of metastable particles, are discussed. The early stage of the afterglow of such a discharge is free of processes involving metastables and has a purely recombination nature. The characteristics of the afterglow are interpreted on the basis of the model taking into account vibrational kinetics and dissociative recombination of molecular ions. A comparison of experimental data and model solutions for collisional-radiative recombination of atomic ions and dissociative recombination leads to the conclusion in favor of the latter process as a source of the excited atoms.

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Reactive collision of electrons with CO+ in cometary coma

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832912 ◽

2018 ◽

Vol 615 ◽

pp. A53 ◽

Cited By ~ 2

Author(s):

Y. Moulane ◽

J. Zs. Mezei ◽

V. Laporta ◽

E. Jehin ◽

Z. Benkhaldoun ◽

...

Keyword(s):

Cross Sections ◽

Vibrational Excitation ◽

Dissociative Recombination ◽

Molecular Data ◽

Molecular Ions ◽

Rate Coefficients ◽

Nuclear Dynamics ◽

Cometary Coma ◽

Reactive Collisions ◽

The Cross

Context. In order to improve our understanding of the kinetics of the cometary coma, theoretical studies of the major reactive collisions in these environments are needed. Deep in the collisional coma, inelastic collisions between thermal electrons and molecular ions result in recombination and vibrational excitation, the rates of these processes being particularly elevated due to the high charged particle densities in the inner region. Aims. This work addresses the dissociative recombination, vibrational excitation, and vibrational de-excitation of electrons with CO+ molecular cations. The aim of this study is to understand the importance of these reactive collisions in producing carbon and oxygen atoms in cometary activity. Methods. The cross-section calculations were based on multichannel quantum defect theory. The molecular data sets, used here to take into account the nuclear dynamics, were based on ab initio R-matrix approach. Results. The cross-sections for the dissociative recombination, vibrational excitation, and vibrational de-excitation processes, for the six lowest vibrational levels of CO+ – relevant for the electronic temperatures observed in comets – are computed, as well as their corresponding Maxwell rate coefficients. Moreover, final state distributions for different dissociation pathways are presented. Conclusions. Among all reactive collisions taking place between low-energy electrons and CO+, the dissociative recombination is the most important process at electronic temperatures characterizing the comets. We have shown that this process can be a major source of O(3P), O(1D), O(1S), C(3P) and C(1D) produced in the cometary coma at small cometocentric distances.

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Dissociative recombination of molecular ions in noble-gas plasmas

Uspekhi Fizicheskih Nauk ◽

10.3367/ufnr.0162.199201b.0035 ◽

1992 ◽

Vol 162 (1) ◽

pp. 35 ◽

Cited By ~ 40

Author(s):

V.A. Ivanov

Keyword(s):

Noble Gas ◽

Dissociative Recombination ◽

Molecular Ions

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Dissociative recombination of electrons and molecular ions

Uspekhi Fizicheskih Nauk ◽

10.3367/ufnr.0136.198201b.0025 ◽

1982 ◽

Vol 136 (1) ◽

pp. 25 ◽

Cited By ~ 48

Author(s):

Aleksandr V. Eletskii ◽

Boris M. Smirnov

Keyword(s):

Dissociative Recombination ◽

Molecular Ions

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Rotational de-excitations of C3H+ (1Σ+) by collision with He: new ab initio potential energy surface and scattering calculations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1086 ◽

2020 ◽

Vol 494 (4) ◽

pp. 5675-5681 ◽

Cited By ~ 1

Author(s):

Sanchit Chhabra ◽

T J Dhilip Kumar

Keyword(s):

Potential Energy ◽

Potential Energy Surface ◽

Ab Initio ◽

Cross Sections ◽

Energy Surface ◽

Molecular Ions ◽

Basis Set ◽

Rate Coefficients ◽

Close Coupling ◽

Collisional Rate Coefficients

ABSTRACT Molecular ions play an important role in the astrochemistry of interstellar and circumstellar media. C3H+ has been identified in the interstellar medium recently. A new potential energy surface of the C3H+–He van der Waals complex is computed using the ab initio explicitly correlated coupled cluster with the single, double and perturbative triple excitation [CCSD(T)-F12] method and the augmented correlation consistent polarized valence triple zeta (aug-cc-pVTZ) basis set. The potential presents a well of 174.6 cm−1 in linear geometry towards the H end. Calculations of pure rotational excitation cross-sections of C3H+ by He are carried out using the exact quantum mechanical close-coupling approach. Cross-sections for transitions among the rotational levels of C3H+ are computed for energies up to 600 cm−1. The cross-sections are used to obtain the collisional rate coefficients for temperatures T ≤ 100 K. Along with laboratory experiments, the results obtained in this work may be very useful for astrophysical applications to understand hydrocarbon chemistry.

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