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.

scholarly journals Mobility of thermal cations in low density alkane gases

1986 ◽  
Vol 64 (12) ◽  
pp. 2423-2426
Author(s):  
Norman Gee ◽  
M. Antonio Floriano ◽  
Gordon R. Freeman
Keyword(s):  
High Temperature ◽  
Momentum Transfer ◽  
Temperature Coefficient ◽  
Cross Sections ◽  
Hard Sphere ◽  
Low Density ◽  
Density Limit ◽  
Average Momentum ◽  
Low Density Limit ◽  
The Cross

Mobilities µ of thermal cations were measured in gases of six linear n-alkanes, ethane to n-decane, and in i-butane and neo-pentane, as functions of density n and temperature T. The low density limit was reached where nµ and the temperature coefficient at constant n, (dnµ,/dT)n, were constant. At all temperatures the average momentum transfer cross sections σave equalled (1.2 ± 0.4) times the cross sections expected from simple polarization. At high temperature σave might be approaching a hard sphere limit.

Formation of CO+ by radiative association II

2020 ◽  
Vol 492 (3) ◽  
pp. 3794-3802
Author(s):  
Martina Zámečníková ◽  
Magnus Gustafsson ◽  
Gunnar Nyman ◽  
Pavel Soldán
Keyword(s):  
Oxygen Atom ◽  
Cross Sections ◽  
Rate Coefficient ◽  
Total Rate ◽  
Temperature Range ◽  
Sn 1987A ◽  
Semiclassical Methods ◽  
Radiative Association ◽  
The Cross

ABSTRACT Radiative association of an oxygen atom with a carbon cation is investigated using quantal and semiclassical methods. The total rate coefficient for spontaneous radiative association of O(2s22p4, 3P) with C+(2s22p, 2P) on the doublet manifold is determined from the corresponding cross-sections. The cross-sections for the ${\rm 1}^2\, \Sigma ^-\rightarrow {\rm A}^2\Pi$, ${\rm 2}^2\, \Sigma ^-\rightarrow {\rm A}^2\Pi$, and ${\rm C}^2\, \Delta \rightarrow {\rm A}^2\Pi$ continuum-bound processes are calculated either semiclassically, in combination with the Breit–Wigner approach, or fully quantum mechanically. In the temperature range 10–10 000 K, our recommended total rate coefficient, obtained from these calculations and the data of Zámečníková et al. (2019), slowly increases from 7.5 × 10−18 cm3s−1 to 2.1 × 10−17 cm3s−1. Corresponding aspects of the CO+ and CO formations in SN 1987A are discussed.

scholarly journals Formation of CO+ by radiative association

2019 ◽  
Vol 489 (2) ◽  
pp. 2954-2960 ◽  
Author(s):  
Martina Zámečníková ◽  
Pavel Soldán ◽  
Magnus Gustafsson ◽  
Gunnar Nyman
Keyword(s):  
Cross Sections ◽  
Formation Rate ◽  
Transition Dipole Moment ◽  
Basis Set ◽  
Rate Coefficients ◽  
Charge Transfer Reaction ◽  
Transition Dipole ◽  
Sn 1987A ◽  
Radiative Association ◽  
Structure Calculations

ABSTRACT We theoretically estimate formation rate coefficients for CO+ through the radiative association of C+(2P) with O(3P). In 1989, Petuchowski et al. claimed radiative association to be the most important route for CO+ formation in SN 1987A. In 1990, Dalgarno, Du and You challenged this claim. Therefore, in this study, we improve previous estimates of the radiative association rate coefficients for forming CO+ from C+(2P) and O(3P). To do this, we perform quantum mechanically based perturbation theory calculations as well as semiclassical calculations, which are combined with Breit–Wigner theory in order to add the effect of shape resonances. We explicitly include four electronic transitions. The required potential energy and transition dipole-moment curves are obtained through large basis set multireference configuration interaction electronic structure calculations. We report cross-sections and from these we obtain rate coefficients in the range of 10 –10 000 K, finding that the CO+ formation rate coefficient is larger than the previous estimate by Dalgarno et al. Still our results support their claim that in SN 1987A, CO is mainly formed through radiative association and not through the charge transfer reaction CO+ + O → CO + O+ as earlier suggested by Petuchowski et al.

scholarly journals Corrigendum

2020 ◽  
Vol 18 (1) ◽  
pp. 75-75
Author(s):  
E Editorial
Keyword(s):  
Electron Impact ◽  
Cross Section ◽  
Cross Sections ◽  
Impact Excitation ◽  
Rate Coefficients ◽  
Electron Impact Excitation ◽  
Ordinate Axis ◽  
The Cross ◽  
Font Color ◽  
Corrected Figure

The Editor-in-Chief has been informed that in the article ?Comparisons of Quantemol and Morgan LXCat cross section sets for electron-neutral scattering and rate-coefficients: helium and water?, FACTA UNIVERSITATIS, Series Physics, Chemistry and Technology Vol. 17, No 2, 2019, pp. 145-159, DOI: https://doi.org/10.2298/FUPCT1902145M, the cross sections for electron-impact excitation of helium in Figure 1b) are wrongly presented. The values of the cross section in the ordinate axis are marked in the interval from 10-1 to 101 (in units 10-16 cm2), and should be from 10-2 to 100. We apologize for that oversight. After further discussion with the corresponding author, the Editor-in-Chief has decided to publish a corrigendum with corrected Figure 1. Link to the corrected article: https://doi.org/10.2298/FUPCT1902145M <br><br><font color="red"><b> Link to the corrected article <u><a href="http://dx.doi.org/10.2298/FUPCT1902145M">10.2298/FUPCT1902145M</a></b></u>

Disorientation of K(42P1/2) Atoms, Induced in Collisions with Noble Gases

1975 ◽  
Vol 53 (15) ◽  
pp. 1499-1503 ◽  
Author(s):  
B. Niewitecka ◽  
L. Krause
Keyword(s):  
Cross Sections ◽  
Noble Gas ◽  
Zero Magnetic Field ◽  
Degree Of Polarization ◽  
Low Density ◽  
Resonance Fluorescence ◽  
Circularly Polarized ◽  
Potassium Vapor ◽  
The Cross ◽  
Gas Pressures

The cross sections for disorientation of 42P1/2 potassium atoms, induced in collisions with noble gas atoms, have been determined in zero magnetic field by studying the depolarization of K(7699 Å) resonance fluorescence in relation to noble gas pressures. Potassium vapor at low density, mixed with a noble gas in a fluorescence vessel, was irradiated with circularly polarized 7699 Å potassium resonance radiation and the resulting resonance fluorescence, observed in an approximately backward direction, was analyzed with respect to circular polarization. The variation of the degree of polarization with gas pressure was interpreted on the basis of a 'J randomization' model for the collisions and yielded the following disorientation cross sections which are appropriately corrected for the effect of nuclear spin: K–He, 24 ± 4 Å2; K–Ne, 21 ± 3 Å2; K–Ar, 37 ± 5 Å2; K–Kr, 51 ± 7 Å2; K–Xe, 69 ± 9 Å2. The cross sections are significantly smaller than values obtained previously in kilogauss fields.

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.

scholarly journals Supernovae and the Galactic Ecosystem

2013 ◽  
Vol 9 (S296) ◽  
pp. 273-281 ◽  
Author(s):  
Q. Daniel Wang
Keyword(s):  
Galaxy Formation ◽  
Supernova Remnants ◽  
Theoretical Work ◽  
Low Density ◽  
Feedback Process ◽  
Hot Gas ◽  
Stellar Feedback ◽  
Galaxy Formation And Evolution ◽  
Formation And Evolution ◽  
The Impact

AbstractSupernovae are the dominant source of stellar feedback, which plays an important role in regulating galaxy formation and evolution. While this feedback process is still quite uncertain, it is probably not due to individual supernova remnants as commonly observed. Most supernovae likely take place in low-density, hot gaseous environments, such as superbubbles and galactic bulges, and typically produce no long-lasting bright remnants. I review recent observational and theoretical work on the impact of such supernovae on galaxy ecosystems, particularly on hot gas in superbubbles and galactic spheroids.

Resonant Transfer Excitation of Fluorine-Like Mo33+ Ion

2010 ◽  
Vol 65 (6-7) ◽  
pp. 599-605
Author(s):  
Hassan Ramadan ◽  
Sabbah Elkilany
Keyword(s):  
Cross Sections ◽  
Impulse Approximation ◽  
Dielectronic Recombination ◽  
Rate Coefficients ◽  
Excitation Process ◽  
Average Scheme ◽  
Quantum Numbers ◽  
Smooth Change ◽  
Overlapped Peaks ◽  
The Cross

Dielectronic recombination (DR) cross sections (σDR) and rate coefficients (αDR) for Mo33+ are calculated using the angular momentum average scheme (AMA). Moreover, the resonant transfer excitation followed by X-ray emission (RTEX) cross sections (σ RTEX) for the collision of Mo33+ with H2 and He targets are calculated and studied. The calculations of the cross sections are performed for both K- and L-shell excitations. A smooth change with the temperatures for αDR is found for all kinds of excitations. The rates for K-shell excitation are very small in comparison with the rates for Lshell excitation. The RTEX cross sections for Mo33+ ions are obtained from their corresponding DR cross sections by the method of folding in the impulse approximation (IMA). σ RTEX for the K-shell excitation shows two overlapped peaks which may be attributed to the two groups in this excitation process. The present calculations are considered as a database for future comparison with theoretical and experimental data using other coupling schemes. Multiple Auger channels are complicating the dependence of the cross sections on principal quantum numbers.

scholarly journals Formation of the BeH+ and BeD+ Molecules in Be+ + H/D Collisions Through Radiative Association

2021 ◽  
Vol 8 ◽  
Author(s):  
Péter Szabó ◽  
Szabolcs Góger ◽  
Magnus Gustafsson
Keyword(s):  
Cross Sections ◽  
Local Thermodynamic Equilibrium ◽  
Kinetic Modelling ◽  
Rate Coefficients ◽  
Mechanical Perturbation ◽  
Equilibrium Limit ◽  
Molecule Formation ◽  
Radiation Fields ◽  
Radiative Association ◽  
Strong Radiation

Cross sections and rate coefficients for the formation of BeH+ and BeD+ molecules in Be+ + H/D collisions through radiative association are calculated using quantum mechanical perturbation theory and Breit-Wigner theory. The local thermodynamic equilibrium limit of the molecule formation is also studied, since the process is also relevant in environments with high-density and/or strong radiation fields. The obtained rate coefficients may facilitate the kinetic modelling of BeH+/BeD+ production in astrochemical environments as well as the corrosion chemistry of thermonuclear fusion reactors.

The scattering states of HD +

1978 ◽  
Vol 358 (1694) ◽  
pp. 321-333 ◽  
Keyword(s):  
Charge Transfer ◽  
Numerical Solution ◽  
Cross Sections ◽  
Quantum Mechanical ◽  
Nuclear Motion ◽  
Hydrogen Atoms ◽  
Mechanical Method ◽  
First Order ◽  
Scattering States ◽  
Quantum Mechanical Method

Elastic and charge-transfer cross-sections for collisions of protons (or deuterons) with deuterium (or hydrogen) atoms have been calculated for 31 values of the energy from 0.001 to 7.5 eV. They were obtained by a fully quantum mechanical method. The internuclear potentials obtained from the Born-Oppenheimer separation were improved by the addition of the first order corrections for nuclear motion, and accurate phase shifts were obtained by numerical solution of a pair of coupled radial Schrödinger equations. The cross-sections are compared with experimental and theoretical values obtained previously.

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