A Novel Merged-Beam Apparatus for Studying Anion-Neutral Reactions

POSTER

Abstract

We have developed a novel apparatus at the Columbia Astrophysics Laboratory to study anion-neutral reactions. Beginning with an anion beam, we use photodetachment to generate a self-merged, anion- neutral beams arrangement. Laboratory beam energies are in the keV range. Because the beams run co-linear, center-of-mass energies from the meV to keV range are achievable. Our proof-of-principle measurement is the associative detachment (AD) reaction ${\rm H}^- + {\rm H} \to {\rm H}_2 + {\rm e}^-$. Published values for this process differ by almost an order of magnitude. With theory and experiment unable to reach a consistent description for this fundamental molecular formation reaction, it raises questions of how can we expect to do better for anion-neutral reactions involving more complicated systems? Measurements using our novel apparatus will help to resolve this fundamental issue in physics and chemistry. We observe the AD reaction by detecting fast H$_2^+$ ions formed through ionizing collisions of the AD-generated H$_2$ with He inside a gas cell. Here we present the current status of the project and discuss our future plans.

Authors

  • K. Miller

    • Columbia University

  • H. Bruhns

    • Columbia University

  • H. Kreckel

    • Columbia University

  • M. Lestinsky

    • Columbia University

  • W. Mitthumsiri

    • Columbia University

  • B. Schmitt

    • Columbia University

  • M. Schnell

    • Columbia University

  • B. Seredyuk

    • Columbia University

  • D.W. Savin

    • Columbia University

  • X. Urbain

    • Universite Catholique de Louvain

  • M.E. Bannister

    • Oak Ridge National Laboratory

  • R. Rejoub

    • Oak Ridge National Laboratory
    • Oak Ridge National Lab, Oak Ridge, TN 37831-6372

  • A. Dorn

    • Max Planck Institute for Nuclear Physics

  • M.L. Rappaport

    • Weizmann Institute of Science