scholarly journals Inelastic collisions in para-H2: Translation-rotation state-to-state rate coefficients and cross sections at low temperature and energy

2005 ◽  
Vol 122 (6) ◽  
pp. 064313 ◽  
Author(s):  
B. Maté ◽  
F. Thibault ◽  
G. Tejeda ◽  
J. M. Fernández ◽  
S. Montero
Keyword(s):  
Low Temperature ◽  
Cross Sections ◽  
Inelastic Collisions ◽  
Rate Coefficients ◽  
State Rate

Rotational cross sections and rate coefficients of CP ( X 2 Σ + ) $\mathrm{CP}(\mathrm{X}^{2}\varSigma ^{+})$ induced by its collision with He ( 1 S ) $\mathrm{He}(^{1}S)$ at low temperature

2018 ◽  
Vol 363 (3) ◽  
Author(s):  
Théophile Tchakoua ◽  
Mama Pamboundom ◽  
Berthelot Said Duvalier Ramlina Vamhindi ◽  
Serge Guy Nana Engo ◽  
Ousmanou Motapon ◽  
...  
Keyword(s):  
Low Temperature ◽  
Cross Sections ◽  
Rate Coefficients

Inelastic rate coefficients for collisions of C4H− with H2

2021 ◽  
Author(s):  
Christian Balança ◽  
Ernesto Quintas-Sánchez ◽  
Richard Dawes ◽  
Fabien Dumouchel ◽  
François Lique ◽  
...  
Keyword(s):  
Cross Sections ◽  
Rotational Level ◽  
Carbon Chain ◽  
Rate Coefficients ◽  
Thermodynamical Equilibrium ◽  
Close Coupling ◽  
State Approximation ◽  
Explicitly Correlated ◽  
State Rate ◽  
Chemical Conditions

Abstract Carbon-chain anions were recently detected in the interstellar medium. These very reactive species are used as tracers of the physical and chemical conditions in a variety of astrophysical environments. However, the Local Thermodynamical Equilibrium conditions are generally not fulfilled in these environments. Therefore, collisional as well as radiative rates are needed to accurately model the observed emission lines. We determine in this work the state-to-state rate coefficients of C4H− in collision with both ortho- and para-H2. A new ab initio 4D potential energy surface was computed using explicitly-correlated coupled cluster procedures. This surface was then employed to determine rotational excitation and de-excitation cross sections and rate coefficients for the first 21 rotational levels (up to rotational level j1 = 20) using the close-coupling method, while the coupled-state approximation was used to extend the calculations up to j1 = 30. State-to-state rate coefficients were obtained for the temperature range 2–100 K. The differences between the ortho- and para-H2 rate coefficients are found to be small.

Cross sections and low temperature rate coefficients for the H + CH+reaction: a quasiclassical trajectory study

2007 ◽  
Vol 9 (5) ◽  
pp. 582-590 ◽  
Author(s):  
Philippe Halvick ◽  
Thierry Stoecklin ◽  
Pascal Larrégaray ◽  
Laurent Bonnet
Keyword(s):  
Low Temperature ◽  
Cross Sections ◽  
Rate Coefficients ◽  
Temperature Rate

Rotational cross sections and rate coefficients of aluminium monoxide AlO(X2Σ+) induced by its collision with He(1S) at low temperature

2018 ◽  
Vol 701 ◽  
pp. 15-21
Author(s):  
Théophile Tchakoua ◽  
Pierre René Nkot Nkot ◽  
Jean Jules Fifen ◽  
Mama Nsangou ◽  
Ousmanou Motapon
Keyword(s):  
Low Temperature ◽  
Cross Sections ◽  
Rate Coefficients

Rotationally inelastic collisions of orbitally degenerate molecules; maser action in OH and CH

1979 ◽  
Vol 368 (1732) ◽  
pp. 99-123 ◽  
Keyword(s):  
Low Temperature ◽  
Cross Section ◽  
Cross Sections ◽  
Born Approximation ◽  
Open Shell ◽  
Inelastic Collisions ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation ◽  
The Cross ◽  
Maser Action

The theory of rotationally inelastic collisions between orbitally degenerate diatomic molecules and open-shell atoms is developed. Because of the orbital degeneracy two or more electronic potential energy surfaces are involved. Matrix elements of the interaction Hamiltonian are given, hyperfine coupling in the diatomic molecule also being included. From these it is apparent th at the parity of the initial Λ -doublet level will influence the inelastic scattering cross section for poles of interaction λ such that λ ≥ 2 Λ .An expression is developed for state-to-state cross sections using the restricted distorted wave Born approximation. A set of branching coefficients is defined which allows the representation of the parity dependence of the cross section in a simple parametric form. The theory is applied to collisional pumping as an excitation mechanism for interstellar maser action of OH and CH through the inversion of Λ -doublet populations. H atoms, H 2 , He, H + and H + 3 are considered as collision partners. Branching coefficients are tabulated for a variety of excitations from the rotational ground states. The sense of the parity dependence of the cross sections arises from the gross features of the interaction potential at medium and long range, and can be deduced using approximate theoretical surfaces or empirical models. An analogy is drawn with the experimental rates of rotational energy transfer in the closely related system H + NH 2 (Ã, 2 A 1 ), which are ca. 10 -9 cm 3 s -1 , and which have been successfully interpreted using the distorted wave Born approximation. These results are used to give qualitative predictions of population inversion in the Λ -doublets of OH, OD and CH in interstellar clouds. We show th at the ground J = 1 ½ doublet, and excited doublets of the F 1 manifold, of OH and OD will be inverted following collisions with H, H 2 and He. The J = 1/2 doublet of the F 2 manifold of OH and OD will be inverted by collisions with the ions H + and H + 3 . In CH low temperature collisions with H atoms will result in inversion of the ground J = 1 ½ doublet. Collisions with H 2 and He at low temperature result in cooling of the doublet. Implications for maser action are briefly discussed.

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.

Sign in / Sign up

Export Citation Format

Share Document