title: Polyatomic ab Initio Complex Potential Energy Surfaces: Illustration of Ultracold Collisions.
abstract: Resonances are metastable states that decay after a finite period of time. These states play a role in many physical processes. For example, in recent cold collision experiments, autoionization from a resonance state was observed. Complementing such observations with theory provides insight into the reaction dynamics under study. Theoretical investigation of autoionization processes is enabled via complex potential energy surfaces (CPESs), where the real and imaginary parts, respectively, provide the energy and decay rate of the system. Unfortunately, calculation of ab initio polyatomic CPESs are cumbersome; hence, they are not in abundance. Here, we present an ab initio polyatomic CPES utilizing a recently developed approach, which makes such calculations feasible. This CPES helps interpret the autoionization process observed in the He(23S) + H2collision. From the behavior of the calculated CPES we can conclusively determine the nature of the autoionization process. Moreover, this CPES was used to generate reaction rates for the collision of He with ortho- and para-H2. These reaction rates are obtained from first principles. The results show a remarkable agreement with the cold collision experimental measurements, which demonstrates the robustness of our method. Hereby, we provide a computational tool for designing and interpreting new types of experiments that involve resonance states, e.g., in nucleobase damages (DNA or RNA) or in interatomic (intermolecular) Coulombic decay.
authors.affiliation: Schulich Faculty of Chemistry, §Department of Physics, and ∥Russell-Berrie Nanotechnology Institute, Technion-Israel Institute of Technology , Haifa 32000, Israel.
authors.forename: Debarati
authors.identifier: http://orcid.org/0000-0001-6986-848X
authors.initials: D
authors.lastname: Bhattacharya
authors.affiliation: Schulich Faculty of Chemistry, §Department of Physics, and ∥Russell-Berrie Nanotechnology Institute, Technion-Israel Institute of Technology , Haifa 32000, Israel.
authors.forename: Anael
authors.initials: A
authors.lastname: Ben-Asher
authors.affiliation: Schulich Faculty of Chemistry, §Department of Physics, and ∥Russell-Berrie Nanotechnology Institute, Technion-Israel Institute of Technology , Haifa 32000, Israel.
authors.forename: Idan
authors.initials: I
authors.lastname: Haritan
authors.affiliation: Faculty of Chemistry, Nicolaus Copernicus University in Toruń , Gagarina 7, 87-100 Toruń, Poland.
authors.forename: Mariusz
authors.initials: M
authors.lastname: Pawlak
authors.affiliation: Schulich Faculty of Chemistry, §Department of Physics, and ∥Russell-Berrie Nanotechnology Institute, Technion-Israel Institute of Technology , Haifa 32000, Israel.
authors.forename: Arie
authors.initials: A
authors.lastname: Landau
authors.affiliation: Schulich Faculty of Chemistry, §Department of Physics, and ∥Russell-Berrie Nanotechnology Institute, Technion-Israel Institute of Technology , Haifa 32000, Israel.
authors.forename: Nimrod
authors.initials: N
authors.lastname: Moiseyev
mesh_terms: D006371:Helium / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D011789:Quantum Theory; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D006371:Helium; D006859:Hydrogen