Statistical analysis of mass-spectrometry-based secondary-ion counting data: Characterization of nanoscale ultrafast secondary-ion emission phenomena triggered by energetic large-cluster impacts on solids.

The complex and interrelated ultrafast phenomena of intense secondary-ion (SI) emission triggered by nanoscale energy deposition by energetic impacts of large-cluster ions of buckminsterfullerene (C_{60}) on solid targets are characterized through a statistical analysis of their mass-analyzed SI counting data. In this study, substituted benzylpyridinium ions, which are important "thermometer" ions, are used as a target to examine energy deposition phenomena at the point and moment that SIs are emitted from the target surface upon each impact. In addition, time-of-flight mass-analyzed SIs emitted under single-impact conditions are counted using an event-by-event counting system to obtain the flight-time data for each impact event. Subsequently, the counting data are analyzed using a newly developed analytical model, based on our previous finding that the probability distribution for the number of emitted SIs induced by each C_{60} ion impact follows a Poisson distribution, to statistically derive underlying information on the phenomena involved. Based on the information obtained by the statistical analysis, we finally present a detailed picture of SI emission phenomena that have been difficult to elucidate using conventional experimental and analytical methods.