SAMOP 2021 – scientific programme

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MO: Fachverband Molekülphysik

MO 5: Miscellaneous

MO 5.1: Talk

Thursday, September 23, 2021, 10:45–11:00, H2

Dissociative recombination of OH⁺ at the Cryogenic Storage Ring — •Ábel Kálosi^1,2, Klaus Blaum², Lisa Gamer², Manfred Grieser², Robert von Hahn², Leonard W. Isberner^2,3, Julia I. Jäger², Holger Kreckel², Daniel Paul², Daniel W. Savin¹, Viviane C. Schmidt², Andreas Wolf², and Oldřich Novotný² — ¹Columbia Astrophysics Laboratory, Columbia University, New York, 10027 New York, USA — ²Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany — ³I. Physikalisches Institut, Justus-Liebig-Universität Gießen, 35392 Gießen, Germany

The cosmic-ray ionization rate (CRIR) of atomic H is an important parameter for diffuse interstellar cloud models. The protons from hydrogen ionization by cosmic rays initiate subsequent ion-molecule reactions that lead to the gas-phase formation of complex molecules. OH⁺ forms early in this chain of reactions, but it can be destroyed via dissociative recombination (DR) with free electrons. The combination of chemical models and astronomical observations of OH⁺ enables one to quantitatively estimate the CRIR in diffuse interstellar clouds. Such models require rate coefficients that account for the internal excitation of the reactants. We have stored fast OH⁺ ion beams in the cryogenic environment of CSR, where infra-red active diatomic hydrides will relax to their lowest rotational states within minutes of storage. Here, we present merged beams DR experiments for OH⁺ interacting with free electrons produced in a low-energy electron cooler, probing collisions at translational temperatures as low as ∼ 10 K.