Formation of Polyatomic Molecules at Low Energies: Three-Body Recombination, Radiative Association, and Photoassociation

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Three-body recombination (TBR) is the process when three particles (for example, three atoms or small molecules) collide simultaneously and form a chemical bond between two of them (dimer formation). During the process, the third particle leaves the dimer carrying away the extra energy released from the bond formation. This process is of a fundamental importance in chemical reactions at room temperature, in plasma environment (such as plasma in thermonuclear fusion reactors), and in ultra-cold gases near the quantum degeneracy (ultra-cold gases are used, for example, in high-precision metrology). Despite its importance in several branches of physics, an accurate theoretical description of the process has been difficult. In the present project a theoretical method for a quick calculation of the TBR rate constants will be developed and tested. The rate constants are the key characteristics for chemical reactions: They depend on the reacting species and the temperature. In addition, several elementary three-body processes of practical interest (in science and technology) in astrophysics, plasma physics, and chemical physics will be considered. Namely, the three-body recombination of hydrogen-like atoms: H+H+H-H2+H, K+K+K-K2+K, and Rb+Rb+Rb-Rb2+Rb; the laser-assisted processes of the type A+A+A+photon-A3, or A2+A+photon-(trimer photoassociation). Finally, a related problem of radiative association (RA) of tri-atomic molecules at low temperatures relevant to astrophysics will also be considered. More precisely, the association of the H- ion with the most abundant diatomic molecules in the interstellar space, H2 and CO, will be studied. This part of the project may help to discover the H- ion in the interstellar space. The the H- ion plays an important role in processes in cold plasma (such as the interstellar medium or cold regions of thermonuclear reactors). Several broader impacts will emerge from the successful completion of the research outlined in this project: (1) Cross-discipline importance of the developed methods and considered problems (physics, chemistry, astrophysics, plasma physics). (2) An impact that we take seriously is the training of talented graduate students who have the tools needed to tackle state-of-the-art problems in this subject area. (3) The principal investigator of the present project is participating in the Coordinated Research Project (CRP) Atomic and Molecular DATA for State-Resolved Modeling of Hydrogen and Helium and their Isotopes in Fusion Plasma of the International Atomic Energy Agency. The purpose of the CRP is to provide the key characteristics of chemical reactions occurring in the ITER thermonuclear reactor that is currently being build by a team of seven international participants. ITER is an experimental reactor aiming to demonstrate that fusion is the energy source of the future.