Exploring new frontiers for the interaction of trapped anions with photons and atoms.

The study of ion-molecule reactions plays a vital role in cold chemistry, thus implying the need of well-controlled ion ensembles in a cold environment. Ions trapped in multipole radio frequency ion traps, can be cooled via collisions with neutral atoms. Usually the coolant undergoes collisions with a thermal shield mounted on a cryostat attaining temperatures of about 4 K. This lower temperature limit can be overcome, using a laser-cooled buffer-gas localized at the center of the ion cloud or via laser-assisted evaporative cooling. In our hybrid atom-ion trap, the anions O- and OH-, are stored in an octupole radio frequency wire trap and a dense cloud of ultracold buffer-gas (Rubidium) confined in a dark spontaneous-force optical trap (Dark-SPOT). The ions can be overlapped with atoms or a far-threshold photodetachment laser altering the energy distribution of the trapped ions. The ab initio calculations also predict reactive collisions between the ions and atoms, which can be used to probe the effective core potentials used in theoretical studies. By varying the ratio of excited to ground state atoms, the quantum state dependent reactive collisions can be studied. In this contribution, the latest results will be presented.