Determine the source of the short-phase acquisition deficit

Determine the cause of the approximately 40% reduction in 18O counts and poorer crater-averaged precision observed when the short pulse phase is acquired last rather than first in interleaved-pulse ToF-SIMS acquisition.

Background

The supporting-information noise-floor analysis compares three phase configurations on homogeneous thermal SiO2: a 6 ns short phase acquired first, repeated 6 ns phases, and a configuration in which the short phase is acquired last. When the short phase was acquired last, it produced approximately 40% fewer 18O counts and poorer crater-averaged precision than the corresponding configuration with the short phase acquired first.

The reported observation indicates an unresolved phase-order or acquisition-sequence effect that is not explained by counting statistics alone. Resolving its cause would clarify whether the standard ordering of phases is necessary and would improve the design and interpretation of multiphase ToF-SIMS measurements.