Probing surface trapping field effects on dielectric nanoparticles

Charge-interaction-induced surface trapping fields are pivotal in ultrafast dynamics of laser-ionized nanoparticles, steering the surface charge carriers and molecular reactions central to nanoscale catalysis and surface chemistry. Here, we experimentally investigated the trapping fields built on the surface of the isolated SiO₂nanoparticles irradiated by intense femtosecond laser pulses. Employing reaction nanoscopy, we measured laser-intensity-dependent electron and ion emission, distinguishing nanoparticle events from background gas contributions. Our results reveal a near-linear scaling of electron yield with laser intensity for nanoparticle events, contrasting with the exponential dependence observed for gas-phase events, evidencing the trapping-field-induced quenching of the electron emission. The electron emission quenching sensitivity is governed by the near-field-mediated charge density distribution, which varies with the Mie parameter and nanoparticle morphology. Furthermore, we demonstrate that the trapping fields critically steer H⁺₃formation on the nanoparticle surface. These findings offer profound insights into the intricate charge dynamics and regulatory mechanisms governing catalytic reactions on dielectric nanomaterials.