%0 Generic
%A Tauch, Jonas
%C Heidelberg
%D 2021
%F heidok:30105
%R 10.11588/heidok.00030105
%T New approaches for cooling molecular anions to the Kelvin range
%U https://archiv.ub.uni-heidelberg.de/volltextserver/30105/
%X This thesis presents two anion cooling techniques based on their interaction with photons or ultracold atoms, pushing the frontier of anion cooling beyond state-of-the-art experiments. A hybrid atom-ion trap (HAITrap) is presented, combining an octupole radio frequency (rf) trap and a dark spontaneous-force optical trap for rubidium. The anions and atoms are probed via photodetachment tomography, time-of-flight thermometry and saturation absorption imaging, respectively. The anion photodetachment via a focused far-threshold laser beam removes anions selectively by their energy. This thesis reports forced evaporative cooling of OH− via dynamically moving the beam, below 4 Kelvin in 2 seconds. A derived thermodynamic model describes the evolution of anion temperature and number, including the importance of ion-ion thermalization and resulting rf-heating in such traps. It shows experimental and theoretical framework to prepare any anionic specie in a vast energy range. This thesis also reports the sympathetic cooling and the collision dynamics of anions with ultracold rubidium in a HAITrap. The cooling is experimentally demonstrated to 30(2) Kelvin for O− and 135(8) Kelvin for OH−. The different cooling behavior is explained by their dissimilar loss channels, which are identified and quantified. These limitations can be overcome in future experiments, providing a tool to cool anions translationally and internally.