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Thursday, 08 Feb. 2024 |
Video-Recording for any system with MP4-support - Video.mp4 (ca. 380 Mb) |
15:15 – 16:15 |
"Mutual neutralization and decay
processes studied in DESIREE"
Prof. Henning Schmidt
(Fysiukm
/ SU)
Abstract:
Mutual neutralization is the fundamental
process where a pair of
oppositely charged ions collide and, in a
charge transfer process, form
neutral products: (A+) + (B-) → A +
B. To be able to study this process
at low (<100 meV) center-of-mass
energy, also for molecular ions, DESIREE
was constructed as a double electrostatic
ion-beam storage ring. In the
cryogenic environment, the ions can be
stored for more than an hour with
very little external disturbance due to
the low temperature and
exceptional vacuum, giving ions time to
relax spontaneously to their
lowest quantum states or to manipulate the
internal energy distributions
applying laser techniques. While DESIREE
is constructed as a double ring
in order to enable studies of mutual neutralization
and other anion-cation
collision processes, the conditions are
also ideal for studies of the
properties of individual ions. In the
colloquium, DESIREE will be
presented and a number of recent
experiments, their results and
applications will be discussed. Examples
of recent results include: The
role of mutual neutralization in stellar
atmospheres; high-precision
atomic anion spectroscopy; stability of
small doubly charged negative
ions; stability of polycyclic aromatic
hydrocarbons in the interstellar
medium, mutual neutralization in Earth’s
atmosphere6, and mutual
neutralization of “water ions” (H3O+) +
(OH-).
The announcement on indico
<https://indico.fysik.su.se/event/8501>
includes the relevant publications.
About the speaker:
Henning Schmidt is a Professor of Physics
at Stockholm University and
Director of the DESIREE Research
Infrastructure. His research is within
the field of experimental atomic,
molecular and optical physics and is
focused, more specifically, on the
properties of atomic and small
molecular systems and their interactions
with light and other ions, often
with astrophysical applications in mind.
Most of Schmidt’s research
involves stored ion beams, making use of
the fact that the same ion
ensemble may be studied over an extended
period of time. He was involved
in the development of the cryogenic double
ion-beam storage-ring facility
DESIREE from its beginning.
He received his PhD in 1994 from Aarhus
University, Denmark, and came to
Stockholm as a postdoc in 1995. After positions
as Assistant Professor and
Senior Lecturer, he became a Professor in
2011. He was appointed
Infrastructure Director in 2018 when
DESIREE was designated a National
Research Infrastructure by the Swedish
Research Council.