scholarly journals The Formation of Interstellar Molecules via Radiative Association Reactions

1980 ◽  
Vol 87 ◽  
pp. 323-324
Author(s):  
David Smith ◽  
Nigel G. Adams
Keyword(s):  
Rate Coefficients ◽  
Rate Data ◽  
Association Rate ◽  
Interstellar Molecules ◽  
Ion Molecule Reactions ◽  
Radiative Association ◽  
Temperature Dependences ◽  
Association Reaction

The radiative association rate coefficients and their temperature dependences have been estimated for several likely interstellar ion-molecule reactions from laboratory collisional association rate data. They include the CH3+ + H2 and CH3+ + H2O reactions, which we suggest lead to CH4 and CH3OH respectively, and the critical association reaction C+ + H2.

scholarly journals The Formation of Complex Interstellar Molecules by Radiative Association

1980 ◽  
Vol 87 ◽  
pp. 317-321
Author(s):  
E. Herbst
Keyword(s):  
Statistical Theory ◽  
Reaction Rate ◽  
Rate Coefficients ◽  
Association Rate ◽  
Interstellar Molecules ◽  
Temperature Range ◽  
Radiative Association ◽  
Association Reaction ◽  
Three Body ◽  
Good Agreement

A new statistical theory of ion-molecule association reaction rate coefficients has been formulated and found to give good agreement with three-body association rate coefficients studied in the laboratory in the temperature range 100-300 K (Herbst 1979a). The theory indicates that certain radiative association reactions proceed rapidly at low interstellar temperatures to produce complex interstellar molecules, as suggested by Smith and Adams (1978).

Molecular-physics aspects of cold chemistry

2019 ◽  
pp. 82-141
Author(s):  
FrÉdÉric Merkt
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Molecular Physics ◽  
Exothermic Reactions ◽  
Langevin Model ◽  
Ion Molecule Reactions ◽  
Radiative Association ◽  
Association Reaction ◽  
Oppenheimer Approximation ◽  
General Aspects

Molecular-physics aspects of cold chemistry are introduced with the example of few-electron molecules. After a brief overview of general aspects of molecular physics, the solution of the molecular Schrödinger equation is presented based on the Born-Oppenheimer approximation and the subsequent evaluation of adiabatic, nonadiabatic, relativistic and radiative (QED) corrections. Low-temperature chemical phenomena are introduced with the example of ion-molecule reactions, using the classical Langevin model for barrier-free exothermic reactions as reference. Then, methods to generate cold few-electron molecules by supersonic-beam-deceleration methods such as Stark, Zeeman, and Rydberg-Stark decelerations are presented. Two astrophysically important reactions, the reaction between H2 and H2+ forming H3+ and H, a very fast reaction following Langevin-capture going over to quantum-Langevin capture at low temperature, and the radiative association reaction H+ + H forming H2+, a very slow reaction in which quantum effects (shape resonances) become important at low temperatures, are used to illustrate the concepts introduced.

scholarly journals Recent Advances in the studies of Reaction Rates relevant to Interstellar Chemistry

1987 ◽  
Vol 120 ◽  
pp. 1-18
Author(s):  
Nigel G. Adams ◽  
David Smith
Keyword(s):  
Laboratory Data ◽  
Dissociative Recombination ◽  
Reaction Rates ◽  
Rate Coefficients ◽  
Current Status ◽  
Laboratory Measurements ◽  
Interstellar Molecules ◽  
Interstellar Clouds ◽  
Radiative Association ◽  
Molecular Synthesis

The current status of laboratory measurements of the rate coefficients for ionic reactions involved in interstellar molecular synthesis is discussed and the experimental techniques used to acquire such data are briefly described. Examples are given of laboratory data which are being obtained at temperatures close to those of interstellar clouds. Particular attention is given to the results of recent theoretical and experimental work which show that the rate coefficients for the binary reactions of ions with polar molecules at low temperatures are much larger than previously assumed. It is shown how these new developments in experiment and theory are reconciling the differences between predicted and observed abundances for some interstellar molecules. Also briefly discussed are: - the phenomenon of isotope exchange in ion/neutral reactions which explains the apparent enrichment of heavy isotopes in some interstellar molecules, the role of atoms in molecular synthesis, some studies of ion/neutral reactions pertaining to shocked regions of interstellar clouds, ternary association reactions and the analogous radiative association reactions, and recent new laboratory measurements of dissociative recombination coefficients. Finally, some guidance is offered in the proper choice of critical kinetic data for use in interstellar chemical modelling and some further requirements and likely future developments are mentioned.

Reactivity Trends in the Gas Phase Addition of Acetylene to N-protonated Aryl Radical Cations

2020 ◽  
Author(s):  
Oisin Shiels ◽  
P. D. Kelly ◽  
Cameron C. Bright ◽  
Berwyck L. J. Poad ◽  
Stephen Blanksby ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ion Trap ◽  
Radical Cations ◽  
Rate Coefficients ◽  
Similar Process ◽  
Ion Molecule Reactions ◽  
Aromatic Radicals ◽  
Polycyclic Aromatic ◽  
Gas Phase Ion ◽  
Type Radical

<div> <div> <div> <p>A key step in gas-phase polycyclic aromatic hydrocarbon (PAH) formation involves the addition of acetylene (or other alkyne) to σ-type aromatic radicals, with successive additions yielding more complex PAHs. A similar process can happen for N- containing aromatics. In cold diffuse environments, such as the interstellar medium, rates of radical addition may be enhanced when the σ-type radical is charged. This paper investigates the gas-phase ion-molecule reactions of acetylene with nine aromatic distonic σ-type radical cations derived from pyridinium (Pyr), anilinium (Anl) and benzonitrilium (Bzn) ions. Three isomers are studied in each case (radical sites at the ortho, meta and para positions). Using a room temperature ion trap, second-order rate coefficients, product branching ratios and reaction efficiencies are reported. </p> </div> </div> </div>

scholarly journals An ICR Study of an Association Reaction at Low Pressure

1980 ◽  
Vol 87 ◽  
pp. 305-306
Author(s):  
M.J. Mcewan ◽  
V. G. Anicich ◽  
W.T. Huntress ◽  
P. R. Kemperer ◽  
M. T. Bowers
Keyword(s):  
Pressure Range ◽  
Rate Coefficient ◽  
Low Pressure ◽  
Second Order ◽  
Radiative Association ◽  
Association Reaction

An ICR investigation of the association reactionCH3+ + HCN CH3.HCN+has shown the reaction follows second order kinetics over the pressure range 1 × 10-6 to 3 × 10-4 Torr with a rate coefficient of 2 × 10-10 cm3s-1. These results can be interpreted in terms of a saturated 3-body or radiative association mechanism.

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