Monte Carlo analysis of the contributions of long-lived positronium to the spectra of positron-impact-induced secondary electrons measured using an annihilation-gamma-triggered time-of-flight spectrometer

Magnetic bottle Time-of-Flight (ToF) spectrometers can measure the energy spectra of all electrons emitted into a 2π sr solid angle simultaneously, greatly reducing data collection time. When detection annihilation gamma (γ) and electron (e) are used as timing signals for ToF spectrometers, e-γ time difference (e-γ TDS) reflective positron-induced distributions provided times between impact positrons emission gammas short compared to flight electrons. This is typically case since have lifetime in solids (∼100–500 ps) secondary (102 ns 103 ns). However, if positron leaves surface positronium atom (a bound electron–positron state), photons be appreciably delayed due longer ortho-positronium (o-Ps) lifetime. result an TDS having exponential tail with decay constant related o-Ps Here, we present analysis using Monte Carlo model which estimates spectral contributions resulting from annihilations. By removing signal, spectrum Positron Impact-Induced Secondary (PIISE) isolated. Furthermore, our allows estimation intensity providing method fraction that form Ps at surfaces without relying on assumed 100 % emitting calibration.