Rotational excitation of methylidynium (CH+) by helium atom at low temperature

Hammami, K.; Owono, L. C. Owono; Jaı̈dane, N.; Lakhdar, Z. Ben

doi:10.1016/j.theochem.2007.11.038

Cited by 24 publications

(38 citation statements)

References 57 publications

(62 reference statements)

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“…As it is far more difficult to determine rate coefficients for excitation with H 2 , we focus on the rotational excitation by He, another major gas component. This study is thus an extension of an earlier Article published by EDP Sciences (Hammami et al 2008). …”

Section: Introductionmentioning

confidence: 73%

“…of CH + to the He atom, and θ the angle between the two distance vectors (Hammami et al 2008). The collinear CH + ...He geometry corresponds to θ = 0 • while the CH + bond distance was frozen at its value at the experimental equilibrium geometry of the ground X 1 Σ + state, i.e., r = r e = 2.1371 Bohr (Huber & Herzberg 1979).…”

Section: Potential Energy Surfacementioning

confidence: 99%

“…An analysis of the excitation cross sections has been carried out by Hammami et al (2008). It was pointed out in that for energies lower than 600 cm −1 , the cross sections for the transition 0 → 1 are larger than those for 0 → 2 while for energies greater than that, the converse holds.…”

Section: Cross Sectionsmentioning

confidence: 99%

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Rotational excitation of methylidynium (CH⁺) by a helium atom at high temperature

Hammami

Owono

Stäuber

2009

A&A

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Context. The Herschel Space Observatory with its high-resolution instrument HIFI on board will observe the CH + 1 → 0 and 2 → 1 rotational transitions in a wide range of gas temperatures up to 1000 K. Collisional parameters for such temperatures are thus welcome. Aims. We aim to obtain accurate rate coefficients for the collisional excitation of CH + by He for high gas temperatures. Methods. The ab initio coupled-cluster [CCSD(T)] approximation was used to compute the interaction potential energy. Cross sections are then derived in the close coupling (CC) approach and rate coefficients inferred by averaging these cross sections over a Maxwell-Boltzmann distribution of kinetic energies. Results. Cross sections are calculated up to 10 000 cm −1 for J ranging from 0 to 10. Rate coefficients are obtained at high temperatures up to 2000 K.

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Section: Introductionmentioning

confidence: 73%

Section: Potential Energy Surfacementioning

confidence: 99%

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Rotational excitation of methylidynium (CH⁺) by a helium atom at high temperature

Hammami

Owono

Stäuber

2009

A&A

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“…Figures 6-10 show the corresponding de-excitation and excitation rate coefficients as a function of temperature in the range 1 K to 300 K. The excitation rate coefficients increase monotonically as a function of temperature, whereas the de-excitation rate coefficients exhibit small fluctuations between 1 K and 10 K, which are direct consequences of the resonances shown in 1-5. To analyse the differences between our results and those of Hammami et al (2008), we also performed calculations with our surface but this time using the rigid rotor approximation. In Table 2, our two sets of results are compared to those of Hammami et al (2008) for two temperatures 20 and 200 K. In this table, the rate coefficients for the rotational transitions j → j ≤ j of CH + ( j = 5, 4, 3, 2, 1), induced by collisions with 4 He are presented.…”

Section: Resultsmentioning

confidence: 99%

“…On the theoretical side, rotationally inelastic close coupling calculations were performed for this system by Hammami et al (2008), for collision energies ranging from 0 to 2500 cm −1 . However, this study was limited to the rigid rotor approximation and their 2D surface did not include the long-range interactions that, are very important to ionic systems.…”

Section: Introductionmentioning

confidence: 99%

Rotational excitation and de-excitation of CH⁺molecules by⁴He atoms

Turpin¹,

Stoecklin²,

Voronin³

2010

A&A

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We present a quantum mechanical investigation of rotational energy transfer in cold collisions of CH + with 4 He atoms. We use a global 3D potential energy surface obtained using the reproducing Kernel Hilbert Space (RKHS) method. Rotational deactivation transition cross-sections are performed for collision energy ranging from 10 −6 to 3000 cm −1 and the corresponding rotational deactivation and excitation rate coefficients are evaluated for the transitions of levels up to j = 5 and temperatures up to 500 K. We also discuss the validity of the rigid rotor approximation for this collision.

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Rotational excitation of aluminium monofluoride (AlF) by He atom at low temperature

Gotoum

Nkem

Hammami

et al. 2010

Astrophys Space Sci

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We report on the calculation of collision induced rotational excitation cross sections and rate coefficients of AlF by He atom at low temperature. These quantities were obtained by first computing the interaction potential energy surface (PES) of the AlF(X 1 + )-He( 1 S) van der Waals complex at the ab initio Coupled Cluster with Single and Double and perturbative Triple excitations [CCSD(T)] level of theory. The aug-cc-pVQZ Gaussian basis, to which was added a set of bond functions, was used for that purpose. The calculations account for basis set superposition errors (BSSE). The interaction potential presents a minimum of ∼24 cm −1 below the AlF-He dissociation limit. The PES was fitted on a basis of Legendre polynomial functions to allow for the calculation of cross sections in the closecoupling (CC) approach. By averaging these cross sections over a Maxwell-Boltzmann velocity distribution, rate coefficients were inferred at low temperatures (T ≤ 300 K). From our computations, a propensity towards J = 1 transitions is observed.

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Rotational excitation of methylidynium (CH+) by helium atom at low temperature

Cited by 24 publications

References 57 publications

Rotational excitation of methylidynium (CH⁺) by a helium atom at high temperature

Rotational excitation of methylidynium (CH⁺) by a helium atom at high temperature

Rotational excitation and de-excitation of CH⁺molecules by⁴He atoms

Rotational excitation of aluminium monofluoride (AlF) by He atom at low temperature

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Rotational excitation of methylidynium (CH+) by helium atom at low temperature

Cited by 24 publications

References 57 publications

Rotational excitation of methylidynium (CH+) by a helium atom at high temperature

Rotational excitation of methylidynium (CH+) by a helium atom at high temperature

Rotational excitation and de-excitation of CH+molecules by4He atoms

Rotational excitation of aluminium monofluoride (AlF) by He atom at low temperature

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Product

Resources

About

Rotational excitation of methylidynium (CH⁺) by a helium atom at high temperature

Rotational excitation of methylidynium (CH⁺) by a helium atom at high temperature

Rotational excitation and de-excitation of CH⁺molecules by⁴He atoms