Secondary ion statistics and determination of nanocluster (m > 107 amu) ion registration efficiency

The m/q spectra of gold nanocluster ions (NCI) (hDi = 18.1 nm and hmi = 4.6 107 amu) desorbed from nanodispersed targets with 252Cf fission fragments were measured using a tandem time-of-flight mass spectrometer at acceleration of 38 kV. In parallel, the statistics of secondary ions (SI) emitted with NCI from various converters (Au and CsI) were measured and the registration efficiency (RE) of NCI was determined. It was shown that distribution of SI number is most adequately described by the geometric distribution. The resulting values of RE are less by a factor of 1.5–2 than those predicted by the Poisson distribution for the m/q range from 3.1 106 to 8.2 106 amu/e.