Ultrafast light-induced molecular reactions on aerosolized nanoparticles may elucidate early steps in the photoactivity of nanoparticles with potential impact in fields ranging from chemistry and medicine to climate science. In situ morphology discrimination for nanoparticle streams when measuring light-induced reaction yields is crucial, but lacking. Here, we experimentally demonstrate, using the reaction nanoscopy technique, that proton momenta from deprotonation reactions induced by intense femtosecond pulses exhibit clear, distinguishable signatures for single silica nanospheres and their clusters. Our findings are supported by classical trajectory Monte Carlo simulations. The results demonstrate an in situ single-shot discrimination method between reaction yields from photoinduced processes on single particles and their clusters. We find that the ionization of clusters dominates at sufficiently low intensities, providing an explanation to resolve previously observed discrepancies between experimental data and theoretical treatments, which considered only single nanoparticles.

Regarded as the most important ion in interstellar chemistry, the trihydrogen cation, $${{\rm{H}}}_{{{3}}}^{+}$$ H 3 + , plays a vital role in the formation of water and many complex organic molecules believed to be responsible for life in our universe. Apart from traditional plasma discharges, recent laboratory studies have focused on forming the trihydrogen cation from large organic molecules during their interactions with intense radiation and charged particles. In contrast, we present results on forming $${{\rm{H}}}_{{{3}}}^{+}$$ H 3 + from bimolecular reactions that involve only an inorganic molecule, namely water, without the presence of any organic molecules to facilitate its formation. This generation of $${{\rm{H}}}_{{{3}}}^{+}$$ H 3 + is enabled by “engineering” a suitable reaction environment comprising water-covered silica nanoparticles exposed to intense, femtosecond laser pulses. Similar, naturally-occurring, environments might exist in astrophysical settings where hydrated nanometer-sized dust particles are impacted by cosmic rays of charged particles or solar wind ions. Our results are a clear manifestation of how aerosolized nanoparticles in intense femtosecond laser fields can serve as a catalysts that enable exotic molecular entities to be produced via non-traditional routes.

The formation of well-controlled nano/micrometer-sized structures on metallic surfaces enables the modification of their optical and wetting properties. Forming such structures on the surface of biocompatible materials, in particular, can expand their applications in various areas of science and technology. Here we present results on covering tantalum (Ta), a biocompatible material, with complex nanosized structures comprising azimuthally- and radially-directed laser-induced periodic surface structures (LIPSS) by rotating the metallic sample with respect to the polarization direction of the irradiating laser pulses. For the first time, we use a high-repetition rate (150 kHz) fiber-based laser with 37 fs ablating pulses and a central wavelength of 1030 nm to form ripples that are directed both parallel and perpendicular to the laser polarization direction on the surface of Ta. Rotating the target during ablation led to forming two distinct zones of structures. The first zone, around the circumference of the target, consisted of both high- and low-spatial-frequency LIPSS, while in the second zone, at the center of the target, was covered by nanoparticles redeposition. We demonstrate how the formation of such complex structures significantly alters the optical reflectance and wetting characteristics of Ta.

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