title: Adiabatic Variational Theory for Cold Atom-Molecule Collisions: Application to a Metastable Helium Atom Colliding with ortho- and para-Hydrogen Molecules.
abstract: We recently developed an adiabatic theory for cold molecular collision experiments. In our previous application of this theory ( Pawlak, M.; et al. J. Chem. Phys. 2015 , 143 , 074114 ), we assumed that during the experiment the collision of an atom with a diatom takes place when the diatom is in the ground rotational state and is located in a plane. In this paper, we present how the variational approach of the adiabatic theory for low-temperature collision experiments can be used for the study a 5D collision between the atom and the diatomic molecule with no limitations on its rotational quantum states and no plane restrictions. Moreover, we show here the dramatic differences in the measured reaction rates of He(23S1) + ortho/para-H2→ He(1s2) + ortho/para-H2++ e-resulting from the anisotropic long-range interactions in the reaction. In collisions of metastable helium with molecular hydrogen in the ground rotational state, the isotropic potential term dominates the dynamics. When the collision is with molecular hydrogen in the first excited rotational state, the nonisotropic interactions play an important role in the dynamics. The agreement of our results with the latest experimental findings ( Klein , A. ; et al. Nat. Phys. 2017 , 13 , 35 - 38 ) is very good.
authors.affiliation: Faculty of Chemistry, Nicolaus Copernicus University in Toruń , Gagarina 7, 87-100 Toruń, Poland.
authors.forename: Mariusz
authors.identifier: http://orcid.org/0000-0002-2200-8287
authors.initials: M
authors.lastname: Pawlak
authors.affiliation: Department of Chemical Physics, Weizmann Institute of Science , Rehovot 76100, Israel.
authors.forename: Yuval
authors.initials: Y
authors.lastname: Shagam
authors.affiliation: Department of Chemical Physics, Weizmann Institute of Science , Rehovot 76100, Israel.
authors.forename: Ayelet
authors.initials: A
authors.lastname: Klein
authors.affiliation: Department of Chemical Physics, Weizmann Institute of Science , Rehovot 76100, Israel.
authors.forename: Edvardas
authors.initials: E
authors.lastname: Narevicius
authors.affiliation: Schulich Faculty of Chemistry and Faculty of Physics, Technion-Israel Institute of Technology , Haifa 32000, Israel.
authors.forename: Nimrod
authors.initials: N
authors.lastname: Moiseyev