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Collisional energy transfer in the HeH+-H reactive system
Benjamin Desrousseaux1, François Lique1
1LOMC - UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP 1123, F-76063 Le Havre, France.
The Journal of Chemical Physics
|February 24, 2020
Summary
The first molecule, helium hydride ion (HeH+), has its rotational excitation by hydrogen atoms precisely calculated. These new findings are crucial for modeling HeH+ in the early Universe and interstellar medium.
Area of Science:
- Theoretical Chemistry
- Astrophysics
- Quantum Mechanics
Background:
- The helium hydride ion (HeH+) is the first molecule formed in the Universe.
- Recent interstellar detection of HeH+ necessitates understanding its physical and chemical properties.
Purpose of the Study:
- To perform exact quantum time-independent calculations for HeH+ rotational excitation by H collisions.
- To provide accurate collisional cross sections and rate coefficients for HeH+.
Main Methods:
- Exact quantum time-independent scattering calculations.
- Inclusion of reactive and exchange channels.
- Computation of cross sections up to 10,000 cm⁻¹ and rate coefficients up to 500 K.
Main Results:
- Identified strongest collision-induced rotational transitions in HeH+ as Δj = 1.
- Found significant differences compared to previous approximate calculations.
- Determined that H collisions dominate HeH+ excitation for electron fractions below 10⁻⁴.
Conclusions:
- New HeH+-H collisional data are essential for accurate modeling of HeH+ excitation.
- Recommends using these data for astrophysical environments, including the early Universe and interstellar medium.
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