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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)




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.


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