Non-Destructive Identification of Cold and Extremely Localized Single   Molecular Ions
  A simple and non-destructive method for identification of a single molecular ion sympathetically cooled by a single laser cooled atomic ion in a linear Paul trap is demonstrated. The technique is based on a precise determination of the molecular ion mass through a measurement of the eigenfrequency of a common motional mode of the two ions. The demonstrated mass resolution is sufficiently high that a particular molecular ion species can be distinguished from other equally charged atomic or molecular ions having the same total number of nucleons. 
M. Drewsen, A. Mortensen, R. Martinussen, P. Staanum, and J. L.   S{\o}rensen