Abstract
Cold molecular ions are of great interest for applications in cold collision studies, chemistry, precision spectroscopy and quantum technologies. In this context, sympathetic cooling of molecular ions by the interaction with laser-cooled atomic ions is a powerful method to cool their translational motion and achieve translational temperatures in the millikelvin range. Recently, we implemented this method in a surface-electrode ion trap. The flexibility in shaping the trapping potentials offered by the surface-electrode structure enabled us to generate planar bicomponent Coulomb crystals and spatially separate the molecular from the atomic ions. Here, we present a detailed description of the fabrication and simulation of the trap as well as a theoretical and experimental investigation of the structural and energetic properties of the Coulomb crystals obtained in the device. We discuss in more detail the separation of different ion species using static electric fields and explore the effects of trap anharmoncities on the shape of bicomponent crystals.
Highlights
The technology for preparing and controlling cold molecules and molecular ions has made impressive progress over the past years [1,2,3]
First results were already reported in our previous study in which we presented shapes of bicomponent crystals obtained for light and heavy sympathetically cooled ions in the SE trap [29]
We focus on three further aspects: (i) the shape and energetics of the bicomponent crystals as a function of the crystal composition, (ii) details of the experiments, already briefly introduced in [29], to spatially separate the different ion species in the crystals, and (iii) the effect of trap anharmonicities on the crystal shapes
Summary
The technology for preparing and controlling cold molecules and molecular ions has made impressive progress over the past years [1,2,3]. An efficient method applicable to trapped molecular ions is sympathetic cooling of their translational motion through collisions with co-trapped laser-cooled atomic ions leading to the formation of bicomponent Coulomb crystals [1, 16]. This method has been widely used in radiofrequency (RF) traps and is applicable to molecules ranging from diatomics to large biomolecules [1, 17]. It has recently been combined with helium buffer-gas techniques to achieve cooling of the internal molecular degrees of freedom [18]
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