Laser spectroscopy of La^- and anion trapping with a view to laser cooling

Direct laser cooling of negative ions has not yet been achieved. An important potential application of this technique is the use of cooled negative ions to sympathetically cool antiprotons. Antihydrogen, synthesized from cold antiprotons, is suitable for fundamental studies tests of CPT symmetry and the weak equivalence principle with antimatter. During this work, the negative lanthanum ion was identified as a good candidate for laser cooling using in-flight spectroscopy. Lanthanum anions were produced as a beam with a kinetic energy of a few keV and were excited using a tunable laser. The light radiation was superimposed to the ions both in a collinear and in a transverse setup to study the laser cooling transition. Trapping of anions both in a Penning trap and in a Paul trap was demonstrated as a prerequisite to increase the interaction time of anions and light towards the first realization of laser cooling. Detailed studies were performed both traps to find the best conditions for anions capture. All trap parameters were optimized with a view to a high capture efficiency as well as optimal properties of the confined plasma.