Virtual Journal of Laser

We present the preparation and deterministic delivery of a selectable number of externally cold molecular ions. A laser cooled
ensemble of ²⁴Mg⁺ ions subsequently confined in several linear Paul traps inter-connected via a quadrupole guide serves as a cold bath for
a single or up to a few hundred molecular ions. Sympathetic cooling embeds the molecular ions in the crystalline structure.
²⁴MgH⁺ ions that serve as a model system for a large variety of other possible molecular ions, are cooled down close to the Doppler
limit and are positioned with an accuracy of one micrometer. After the production process, severely compromising the vacuum
conditions, the molecular ion is efficiently transferred into nearly background-free environment. The transfer of a molecular
ion between different traps as well as the control of the molecular ions in the traps is demonstrated. Schemes, optimized
for the transfer of a specific number of ions, are realized and their efficiencies are evaluated. This versatile source applicable
for broad charge-to-mass ratios of externally cold and precisely positioned molecular ions can serve as a container-free target
preparation device well suited for diffraction or spectroscopic measurements on individual molecular ions at high repetition
rates (kHz).