A sputter ion source with a solid graphite target has been used to produce dianions with a focus on carbon cluster dianions, Cn2−, with n=7−24. Singly and doubly charged anions from the source were accelerated together to kinetic energies of 10 keV per atomic unit of charge and injected into one of the cryogenic (13 K) ion-beam storage rings of the Double ElectroStatic Ion Ring Experiment facility at Stockholm University. Spontaneous decay of internally hot Cn2− dianions injected into the ring yielded C− anions with kinetic energies of 20 keV, which were counted with a microchannel plate detector. Mass spectra produced by scanning the magnetic field of a 90∘ analyzing magnet on the ion injection line reflect the production of internally hot C72−−C242− dianions with lifetimes in the range of tens of microseconds to milliseconds. In spite of the high sensitivity of this method, no conclusive evidence of C62− was found while there was a clear C72− signal with the expect isotopic distribution. An upper limit is deduced for a C62− signal that is two orders-of-magnitue smaller than that for C72−. In addition, CnO2− and CsCu2− dianions were detected.
@article{arxiv.1804.00233,
title = {Dianion diagnostics in DESIREE: High-sensitivity detection of $\text{C}_{n}^{2-}$ from a sputter ion source},
author = {K. C. Chartkunchand and M. H. Stockett and E. K. Anderson and G. Eklund and M. K. Kristiansson and M. Kamińska and N. de Ruette and M. Blom and M. Björkhage and A. Källberg and P. Löfgren and P. Reinhed and S. Rosén and A. Simonsson and H. Zettergren and H. T. Schmidt and H. Cederquist},
journal= {arXiv preprint arXiv:1804.00233},
year = {2018}
}