An rf-carpet electrospray ion source to provide isobaric mass calibrants   for trans-uranium elements
  For trans-uranium elements, stable atomic isobars do not exist. In order to provide isobaric reference ions for the mass measurement of trans-uranium elements, an electrospray ion source (ESI) was combined with an rf-carpet to collect molecular ions efficiently. The rf-carpet allows for simplification of the pumping system to transport ions from the ESI to a precision mass analyzer. Molecular ions appropriate for isobaric references of trans-uranium elements were extracted from the rf-carpet and analyzed by a multi-reflection time-of-flight mass spectrograph (MRTOF-MS) with a resolving power of $\rm{R_m} \gtrsim100,000$. 
S. Naimi, S. Nakamura, Y. Ito, H. Mita, K. Okada, A. Ozawa, P. Schury,   T. Sonoda, A. Takamine, M. Wada, H. Wollnik
nucl-ex physics.atom-ph