Molecular Systems - Research Projects

Our research group studies the quantum mechanical dynamics of cold molecular few-body systems. We search for quantum effects in the reaction dynamics of ion-molecule reactions, explore strong laser fields for collisions with aligned molecules, and study reactions and photodetachment of cold molecular anions of interstellar importance. Recently, we started developing new schemes for high-resolution terahertz spectroscopy of molecular ions.

Imaging spectrometer

Crossed-beam imaging setup

 

 

Reactive scattering of slow molecules and ions

We investigate the quantum dynamics of prototypical ionic reactions. The goal of this research is to unravel the multidimensional dynamics of systems with several different degrees of freedom. Important model systems are charge transfer reactions and nucleophilic substitution reactions. In the focus of our studies are quantum scattering resonances in few-body collisions and the coupling of spectator vibrational modes to the reactive degrees of freedom. With this work we could unravel several distinct reaction mechanism in good agreement with multi-dimensional chemical dynamics simulations.

 

Reactions and state-resolved photodetachment of cold trapped negative ions

To study negative ion-neutral reactions at very low energies we trap ions at variable temperatures from 8 to 300K in a high-order multipole trap. This 22-pole trap features a large field-free trapping volume with steep walls. With this we study the influence of rotational and hyperfine angular momentum, of tunneling and of the long-range ion-neutral interaction on anion-molecule reactions. Emphasis lies on the study of processes involving interstellar negative ions, such as the first identified interstellar anion C6H-. Both ion-molecule reactions and photodetachment of these systems are of great interest to understand the role and the abundance of anions in the interstellar medium.

Ion trap setup

22-pole rf ion trap setup

 

Terahertz spectroscopy and quantum state-selective collision processes of cold trapped ions

Using photodetachment spectroscopy near threshold we developed a scheme to measure rotational state populations of trapped anions. We currently employ this scheme to study state-selected cold collisions of ions and neutrals. We also use this as a means to study the terahertz absorption of trapped ions, see here for details.

If you are interested to learn more about one of these projects or in joining our team, please contact Roland Wester.

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