Rotational excitation of AlCl induced by H₂ collisions
Abstract
We present the first study of the rotational excitation of AlCl(X¹Σ⁺) induced by collisions with H₂. We have calculated a four dimensional potential energy surface (PES) to describe the AlCl-H₂ interaction, with AlCl and H-2 being treated as rigid rotors. This PES has been computed using the explicitly correlated coupled-cluster method with single, double, and perturbative triple excitation in conjunction with the augmented-correlation consistent-polarized valence triple zeta basis set. Then, we have calculated the rotational excitation cross sections between the first 41 rotational levels of AlCl induced by H₂ collisions using the time-independent quantum mechanical close-coupling and coupled-states formalisms. Convergence tests revealed that the inclusion of excited para-H₂ energy levels in the rotational basis has a minor effect on the magnitude of the excitation cross sections. We also found that AlCl excitation cross sections induced by ortho-H₂ collisions are in good agreement with those induced by para-H₂ collisions. Hence, we limited the calculations to the excitation cross sections induced by H₂ in its ground rotational state. To derive excitation rate coefficients for temperatures up to 250 K, the cross sections computed for energies up to 1500 cm⁻¹ were averaged over a Maxwell-Boltzmann velocity distribution. The new rate coefficients were compared to those available for the AlCl-He collisional system, and major differences were found at high temperature, showing that actual AlCl-H₂ rate coefficients should be used for accurate astrophysical models. The new data are expected to play a crucial role in the modeling of AlCl observational spectra and will help in better constraining its abundance in space.
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BibTeX
@article{mhamdi2026rotational,
title = {{Rotational excitation of AlCl induced by H₂ collisions}},
author = {M. M'Hamdi and A. Ben Houria and C T Bop and N. Jaïdane and K. Hammami and F Lique},
journal = {The Journal of Chemical Physics},
year = {2026},
month = sep,
doi = {10.1063/5.0314746},
url = {https://hal.science/hal-05512501v1},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - Rotational excitation of AlCl induced by H₂ collisions
AU - M. M'Hamdi
AU - A. Ben Houria
AU - C T Bop
AU - N. Jaïdane
AU - K. Hammami
AU - F Lique
PY - 2026
DA - 2026/09/07
JO - The Journal of Chemical Physics
DO - 10.1063/5.0314746
UR - https://hal.science/hal-05512501v1
AB - We present the first study of the rotational excitation of AlCl(X¹Σ⁺) induced by collisions with H₂. We have calculated a four dimensional potential energy surface (PES) to describe the AlCl-H₂ interaction, with AlCl and H-2 being treated as rigid rotors. This PES has been computed using the explicitly correlated coupled-cluster method with single, double, and perturbative triple excitation in conjunction with the augmented-correlation consistent-polarized valence triple zeta basis set. Then, we have calculated the rotational excitation cross sections between the first 41 rotational levels of AlCl induced by H₂ collisions using the time-independent quantum mechanical close-coupling and coupled-states formalisms. Convergence tests revealed that the inclusion of excited para-H₂ energy levels in the rotational basis has a minor effect on the magnitude of the excitation cross sections. We also found that AlCl excitation cross sections induced by ortho-H₂ collisions are in good agreement with those induced by para-H₂ collisions. Hence, we limited the calculations to the excitation cross sections induced by H₂ in its ground rotational state. To derive excitation rate coefficients for temperatures up to 250 K, the cross sections computed for energies up to 1500 cm⁻¹ were averaged over a Maxwell-Boltzmann velocity distribution. The new rate coefficients were compared to those available for the AlCl-He collisional system, and major differences were found at high temperature, showing that actual AlCl-H₂ rate coefficients should be used for accurate astrophysical models. The new data are expected to play a crucial role in the modeling of AlCl observational spectra and will help in better constraining its abundance in space.
SN - 0021-9606
SN - 1089-7690
ER -