48th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 62, Number 8
Monday–Friday, June 5–9, 2017;
Sacramento, California
Session H5: AMO in Astrophysics
10:30 AM–12:30 PM,
Wednesday, June 7, 2017
Room: 310
Chair: Thomas Gorczyca, Western Michigan University
Abstract ID: BAPS.2017.DAMOP.H5.2
Abstract: H5.00002 : Astrochemistry in TSR and CSR Ion Storage Rings
11:00 AM–11:30 AM
Preview Abstract
Abstract
Author:
Oldrich Novotny
(Max Planck Institute for Nuclear Physics)
Dissociative recombination (DR) of molecular ions plays a key role in
controlling the charge density and composition of the cold interstellar
medium (ISM). Experimental data on DR are required in order to understand
the chemical network in the ISM and related processes such as star formation
from molecular clouds. Needed data include not only total reaction cross
sections, but also the chemical composition and excitation states of the
neutral products.
Utilizing the TSR storage ring in Heidelberg, Germany, we have carried out
DR measurements for astrophysically important molecular ions. We use a
merged electron-ion beams technique combined with event-by-event fragment
counting and fragment imaging. The count rate of detected neutral DR
products yields the absolute DR rate coefficient. Imaging the distribution
of fragment distances provides information on the kinetic energy released
including the states of both the initial molecule and the final products.
Additional kinetic energy sensitivity of the employed detector allows for
identification of fragmentation channels by fragment-mass combination within
each dissociation event. Such combined information is essential for studies
on DR of polyatomic ions with multi-channel breakup.
The recently commissioned Cryogenic Storage Ring (CSR) in Heidelberg,
Germany, extends the experimental capabilities of TSR by operation at
cryogenic temperatures down to \textasciitilde 6 K. At these conditions
residual gas densities down to \textasciitilde 100 cm$^{\mathrm{-3}}$ can be
reached resulting in beam storage times of several hours. Long storage in
the cold environment allows the ions to relax down to their rotational
ground state, thus mimicking well the conditions in the cold ISM. A variety
of astrophysically relevant reactions will be investigated at these
conditions, such as DR, electron impact excitation, ion-neutral collisions,
etc.
We report our TSR results on DR of HCl$^{\mathrm{+}}$ and
D$_{\mathrm{2}}$Cl$^{\mathrm{+}}$. We also present first results from the
CSR commissioning experiments.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2017.DAMOP.H5.2