M L Rappaport

Publications (2)1.52 Total impact

• Source

  Available from: columbia.edu

  Article: A novel merged beams apparatus to study anion-neutral reactions.

  H Bruhns, H Kreckel, K Miller, M Lestinsky, B Seredyuk, W Mitthumsiri, B L Schmitt, M Schnell, X Urbain, M L Rappaport, C C Havener, D W Savin
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  ABSTRACT: We have developed a novel laboratory instrument for studying gas phase, anion-neutral chemistry. To the best of our knowledge, this is the first such apparatus which uses fast merged beams to investigate anion-neutral chemical reactions. As proof-of-principle we have detected the associative detachment reaction H(-)+H-->H(2)+e(-). Here we describe the apparatus in detail and discuss related technical and experimental issues.
  The Review of scientific instruments 01/2010; 81(1):013112. · 1.52 Impact Factor
• Article: Reproducing the Molecular Reactions Leading to the Formation of the First Stars

  Daniel Wolf Savin, H. Bruhns, H. Kreckel, M. Lestinsky, K. Miller, W. Mitthumsiri, B. Seredyuk, M. Schnell, X. Urbain, A. Dorn, B. Schmitt, M. E. Bannister, C. C. Havener, O. Heber, M. L. Rappaport
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  ABSTRACT: The dominant formation mechanism of H2 during the epoch of first star and protogalaxy formation is the associative detachment (AD) reaction H + H- forming H2 + e-. Published values for this process differ by almost an order of magnitude. These uncertainties limit our ability to reliably model this epoch of the universe. For example, recent studies have shown that the effect of these uncertainties is particularly large for protogalaxies forming in previously ionized regions, affecting predictions of whether or not a given protogalaxy can cool and condense within a Hubble time and altering the strength of the ultraviolet background that is required to prevent collapse. We have built a novel apparatus at the Columbia University Astrophysics Laboratory to study this reaction. Beginning with an anion beam, we use photodetachment to generate a self-merged, anion-neutral beams arrangement. Laboratory energies are in the keV range. Because the beams co-propagate, center-of-mass energies from the meV to keV range will be achievable. We observe the AD reaction by detecting the fast H2+ ions formed through ionizing collisions of the AD-generated H2 with the background gas in the vacuum chamber. Here we present our recent results and discuss our future plans. This work has been supported in part by the NSF Chemistry Research Instrumentation and Facilities: Instrument Development program.
  12/2008; 41:414.