Investigation of spatial structure and sympathetic cooling in the 9Be+–40Ca+ bi-component Coulomb crystals

Abstract

We study the spatial structure and sympathetic cooling of the bi-component Coulomb crystal (CC), which consists of approximate 450 9Be+ ions and 450 40Ca+ ions with a mass ratio of 0.225 in a segmented linear ion trap. By two-dimensional imaging of the bi-component CC, the 9Be+ ions are found to be surrounded by the 40Ca+ ions in the radial direction with a separation ratio of ∼ 2.0, and the axial length of the 9Be+ ions occupied area is much larger than that of the 40Ca+ ions occupied area. Combined with the previous experimental results, the structure of the 9Be+–40Ca+ CC shows the larger the difference in the mass–charge ratio, the larger the separation between the two species. The comparison of the fluorescence spectra of the 9Be+ ions in the bi-component CC and the pure CC indicates that the 9Be+ ions can be sympathetically cooled and stably localized by the laser-cooled 40Ca+ ions during the recording of the fluorescence spectrum.