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

Science ◽  
2019 ◽  
Vol 365 (6454) ◽  
pp. 676-679 ◽  
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.

Astrochemical studies at the Cryogenic Storage Ring

2019 ◽  
Vol 377 (2154) ◽  
pp. 20180412 ◽  
Author(s):  
H. Kreckel ◽  
O. Novotný ◽  
A. Wolf
Keyword(s):  
Storage Ring ◽  
Nuclear Physics ◽  
Molecular Ions ◽  
Rate Coefficients ◽  
Max Planck ◽  
Electron Recombination ◽  
Interstellar Molecule ◽  
Electron Cooler ◽  
Cryogenic Storage ◽  
Main Research

The new Cryogenic Storage Ring at the Max Planck Institute for Nuclear Physics (Heidelberg, Germany) has recently become operational. One of the main research areas foreseen for this unique facility is astrochemical studies with cold molecular ions. The spontaneous radiative cooling of the prototype interstellar molecule CH + to its lowest rotational states has been demonstrated by photodissociation spectroscopy, paving the way for experiments under true interstellar conditions. To this end, a low-energy electron cooler and a neutral atom beam set-up for merged beams studies have been constructed. These experiments have the potential to provide energy-resolved rate coefficients for fundamental astrochemical processes involving state-selected molecular ions. The main target reactions include some of the key processes of interstellar chemistry, such as the electron recombination of H 3 + , charge exchange between H 2 + and H, or the formation of CH + in collisions of triatomic hydrogen ions and C atoms. This article is part of a discussion meeting issue ‘Advances in hydrogen molecular ions: H 3 + , H 5 + and beyond’.

scholarly journals Dissociative Recombination of CH+ Molecular Ion Induced by Very Low Energy Electrons

Atoms ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 82 ◽  
Author(s):  
Zsolt J. Mezei ◽  
Michel D. Epée Epée ◽  
Ousmanou Motapon ◽  
Ioan F. Schneider
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Incident Energy ◽  
Dissociative Recombination ◽  
Boltzmann Distribution ◽  
Rate Coefficients ◽  
Rotational States ◽  
Low Energy Electrons ◽  
Quantum Defect Theory ◽  
Π State

We used the multichannel quantum defect theory to compute cross sections and rate coefficients for the dissociative recombination of CH + initially in its lowest vibrational level v i + = 0 with electrons of incident energy below 0.2 eV. We have focused on the contribution of the 2 2 Π state which is the main dissociative recombination route at low collision energies. The final cross section is obtained by averaging the relevant initial rotational states ( N i + = 0 , ⋯ , 10 ) with a 300 K Boltzmann distribution. The Maxwell isotropic rate coefficients for dissociative recombination are also calculated for different initial rotational states and for electronic temperatures up to a few hundred Kelvins. Our results are compared to storage-ring measurements.

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

2006 ◽  
Vol 364 (1848) ◽  
pp. 3113-3120 ◽  
Author(s):  
Alexandre Faure ◽  
Laurent Wiesenfeld ◽  
Pierre Valiron ◽  
Jonathan Tennyson
Keyword(s):  
Dissociative Recombination ◽  
Molecular Ions ◽  
Rate Coefficients ◽  
Galactic Centre ◽  
Low Density ◽  
Rotational Excitation ◽  
Astrophysical Plasmas ◽  
Electron Collisions ◽  
Dissociation Dynamics ◽  
Rotational Distribution

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.

scholarly journals Reactive collision of electrons with CO+ in cometary coma

2018 ◽  
Vol 615 ◽  
pp. A53 ◽  
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.

Dissociative recombination of molecular ions in noble-gas plasmas

1992 ◽  
Vol 162 (1) ◽  
pp. 35 ◽  
Author(s):  
V.A. Ivanov
Keyword(s):  
Noble Gas ◽  
Dissociative Recombination ◽  
Molecular Ions

Dissociative recombination of electrons and molecular ions

1982 ◽  
Vol 136 (1) ◽  
pp. 25 ◽  
Author(s):  
Aleksandr V. Eletskii ◽  
Boris M. Smirnov
Keyword(s):  
Dissociative Recombination ◽  
Molecular Ions

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

2020 ◽  
Vol 494 (4) ◽  
pp. 5675-5681 ◽  
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.

Dissociative recombination of the methane family ions: rate coefficients and implications

2004 ◽  
Vol 33 (2) ◽  
pp. 216-220 ◽  
Author(s):  
C.H. Sheehan ◽  
J.-P. St.-Maurice
Keyword(s):  
Dissociative Recombination ◽  
Rate Coefficients

Direct observation of rotational states of molecular ions in photoionization processes

1975 ◽  
Vol 36 (4) ◽  
pp. 495-499 ◽  
Author(s):  
Wm.B. Peatman
Keyword(s):  
Direct Observation ◽  
Molecular Ions ◽  
Rotational States

scholarly journals Spectroscopy and dissociative recombination of the lowest rotational states of H+3

2009 ◽  
Vol 192 ◽  
pp. 012022 ◽  
Author(s):  
A Petrignani ◽  
H Kreckel ◽  
M H Berg ◽  
S Altevogt ◽  
D Bing ◽  
...  
Keyword(s):  
Dissociative Recombination ◽  
Rotational States
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