Reaction Nanoscopy of Ion Emission from Sub-wavelength Propanediol Droplets

TL;DR

This study applies reaction nanoscopy to ionize and analyze propanediol droplets, revealing surface chemistry differences between isomers and demonstrating the technique's potential for observing charge and reaction dynamics on droplets.

Contribution

It introduces reaction nanoscopy for analyzing ion emission from charged nanodroplets and compares isomer-specific surface reactions using ultrashort laser pulses.

Findings

Enhanced methyl cation production from 1,2-PDO droplets

Surface molecule alignment influences ion emission

Technique enables in-situ droplet size and charge characterization

Abstract

Droplets provide unique opportunities for the investigation of laser-induced surface chemistry. Chemical reactions on the surface of charged droplets are ubiquitous in nature and can provide critical insight into more efficient processes for industrial chemical production. Here, we demonstrate the application of the reaction nanoscopy technique to strong-field ionized nanodroplets of propanediol (PDO). The technique's sensitivity to the near-field around the droplet allows for the in-situ characterization of the average droplet size and charge. The use of ultrashort laser pulses enables control of the amount of surface charge by the laser intensity. Moreover, we demonstrate the surface chemical sensitivity of reaction nanoscopy by comparing droplets of the isomers 1,2-PDO and 1,3-PDO in their ion emission and fragmentation channels. Referencing the ion yields to gas-phase data, we find an enhanced production of methyl cations from droplets of the 1,2-PDO isomer. Density functional theory simulations support that this enhancement is due to the alignment of 1,2-PDO molecules on the surface. The results pave the way towards spatio-temporal observations of charge dynamics and surface reactions on droplets in pump-probe studies.