40th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 54, Number 7
Tuesday–Saturday, May 19–23, 2009;
Charlottesville, Virginia
Session S6: Molecular Dissociation Induced by Electron Collisions
2:00 PM–4:00 PM,
Friday, May 22, 2009
Minor Hall
Room: 125
Chair: Chris Greene, University of Colorado
Abstract ID: BAPS.2009.DAMOP.S6.2
Abstract: S6.00002 : Molecular Dissociation Induced by Electron Collisions
2:30 PM–3:00 PM
Preview Abstract
Abstract
Author:
Andreas Wolf
(Max-Planck Institute for Nuclear Physics, Heidelberg)
Free electrons can efficiently break molecules or molecular ions
in low-energy collisions by the processes of dissociative
recombination or attachment. These processes make slow electrons
efficient chemical agents in many environments. For dissociative
recombination, in particular, studies of the underlying reaction
paths and mechanisms have become possible on a uniquely
elementary level in recent years both for theory and experiment.
On the experimental side, collisions can be prepared at resolved
collision energies down to the meV (10 Kelvin) level,
increasingly gaining control also over the initial molecular
quantum level, and individual events are detected and
kinematically analyzed by fast-beam coincidence fragment imaging.
Experiments are reported from the ion cooler ring TSR in
Heidelberg. Stored beams of molecular ions cooled in their
external and internal degrees of freedom are collinearly merged
with intense and cold electron beams from cryogenic GaAs
photocathodes, recently shown to yield fast cooling of the
center-of-mass motion also for heavy and correspondingly slow
molecular ion beams. To reconstruct the molecular fragmentation
events multiparticle imaging can now be used systematically with
collision energies set a wide range, especially aiming at
specific electron capture resonances. Thus, for CF$^+$ it is
found that the electronic state of the C fragment ($^3P$ or
$^1D$) switches resonantly when the collision energy is changed
by only a small fraction. As a new powerful tool, an
energy-sensitive multi-strip surface-barrier detector (EMU) has
been set up to measure with near-unity efficiency the masses of
all fragments together with their hit positions in
high-multiplicity events. Among many uses, this device allows
internal molecular excitations to be derived for individual
chemical channels in polyatomic fragmentation. New results will
be presented in particular on the breakup of the hydronium ion
(D$_3$O$^+$).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.DAMOP.S6.2