An update of and suggested increase in calculated radiative association rate coefficients

1985 ◽  
Vol 291 ◽  
pp. 226 ◽  
Author(s):  
E. Herbst
Keyword(s):  
Rate Coefficients ◽  
Association Rate ◽  
Radiative Association

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).

Radiative charge transfer and radiative association of helium ions with neon atoms

1984 ◽  
Vol 62 (12) ◽  
pp. 1622-1628 ◽  
Author(s):  
D. L. Cooper ◽  
K. Kirby ◽  
A. Dalgarno
Keyword(s):  
Charge Transfer ◽  
Dipole Moments ◽  
Rate Coefficients ◽  
Spin Orbit ◽  
Helium Ions ◽  
Transition Dipole ◽  
Radiative Association ◽  
Transition Dipole Moments ◽  
Spin Orbit Interactions ◽  
Comparison With Experimental Data

Ab initio calculations are carried out for the dipole moments of the X2Σ+, A2Π, and B2Σ+ states of HeNe+, and the transition dipole moments connecting them. The effects of spin-orbit interactions are explored briefly. The transition dipole moments are used in a calculation of the rate coefficients of radiative charge transfer and radiative association of He+ ions in neon and the associated spectra are obtained. Comparison with experimental data provides support for the conclusion that the radiation detected was emitted in the course of the collisions of He+ with Ne. Some quantitative discrepancies remain which may arise from intensity stealing by the A22Π1/2 state from the X2Σ+ state.

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.

Radiative association for the formation of MgO

2020 ◽  
Vol 500 (2) ◽  
pp. 2496-2502
Author(s):  
Tianrui Bai ◽  
Zhi Qin ◽  
Linhua Liu
Keyword(s):  
Cross Sections ◽  
Rate Coefficients ◽  
Low Density ◽  
Mechanical Method ◽  
Hot Gas ◽  
Radiative Association ◽  
Quantum Mechanical Method ◽  
Formation And Evolution ◽  
The Cross ◽  
Increasing Temperature

ABSTRACT The radiative association process for the formation of magnesium oxide (MgO) may be of great importance due to its frequent occurrence in the low-density and dust-poor astrochemical environments. In this work, the cross-sections and rate coefficients for the A1Π → X1Σ+, ${\rm X}^1\Sigma ^+\, \rightarrow \, {\rm A}^1\Pi$, D1Δ → A1Π, a3Π → e3Σ−, ${\rm X}^1\Sigma ^+\, \rightarrow \, {\rm X}^1\Sigma ^+$, and A1Π → A1Π radiative association processes of forming MgO are theoretically estimated. The cross-sections for the transitions between the different states are obtained by using the semiclassical method for direct contributions and the Breit–Wigner theory as a complement for resonance contributions. For the transitions between the same states, the quantum mechanical method is used. The rate coefficients are then obtained from the cross-sections for the temperatures in the range of 10–10 000 K and the results are found to vary from 4.69 $\times \, 10^{-16}$ to 6.27 $\times \, 10^{-14}$ cm3 s−1. For temperatures lower than around 693 K, the rate coefficients for the A1Π → X1Σ+ process are dominant, which indicates this process is the most efficient way of producing MgO at low temperatures. However, the rate coefficients for the D1Δ → A1Π process go through a rapid increase with increasing temperature and become dominant at higher temperatures. For other processes, their rate coefficients are several orders of magnitude lower than those for the two processes mentioned above. The results can be used to further investigate the formation and evolution of MgO in low density and hot gas close to the photosphere of evolved oxygen-rich stars.

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