Sympathetic cooling of molecular ions: multi-species Coulomb crystals and chemical reactions

This paper reports on two experimental setups that allow the cooling of molecular ions over a wide molecular mass range. In the experiments they use ¹³⁸Ba⁺ and ⁹Be as directly laser cooled ion species. ⁹Be⁺ is used as coolant for very light molecules, in particular molecular hydrogen ions. ¹³⁸Ba+ can cool small di-and triatomic molecules and also offers the prospect of cooling complex, highly charged molecules with masses up to 20000 amu.