title: Sympathetic cooling of molecular ions in selected rotational and vibrational states produced by threshold photoionization.
abstract: We present a new method for the generation of rotationally and vibrationally state-selected, translationally cold molecular ions in ion traps. Our technique is based on the state-selective threshold photoionization of neutral molecules followed by sympathetic cooling of the resulting ions with laser-cooled calcium ions. Using N₂(+) ions as a test system, we achieve >90% selectivity in the preparation of the ground rovibrational level and state lifetimes on the order of 15 minutes limited by collisions with background-gas molecules. The technique can be employed to produce a wide range of apolar and polar molecular ions in the ground and excited rovibrational states. Our approach opens up new perspectives for cold quantum-controlled ion-molecule-collision studies, frequency-metrology experiments with state-selected molecular ions and molecular-ion qubits.
authors.affiliation: Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland.
authors.forename: Xin
authors.initials: X
authors.lastname: Tong
authors.forename: Alexander H
authors.initials: AH
authors.lastname: Winney
authors.forename: Stefan
authors.initials: S
authors.lastname: Willitsch