Inferring the lifetime of the ionic liquid monomer EMI+ in electrospray plumes from numerical and theoretical analyses

ATM Tahsin and E Petro, JOURNAL OF APPLIED PHYSICS, 137, 193303 (2025).

DOI: 10.1063/5.0253889

This study explores the applicability of reactive molecular dynamics and the transition state theory to develop a thermal fragmentation model for the positive ionic liquid monomer, 1-ethyl-3-methylimidazolium (EMI+ ). The mean lifetime of the monomer is described as a function of temperature and the external electric field. The products of the thermal dissociation of EMI(+)are analyzed to better understand the fragmentation mechanism and its dependencies on internal and external factors, such as internal energy thermodynamics and external electric field, respectively. The study also explores a first-order theoretical analysis of the electrospray emission process to estimate the post- emission temperature of EMI+. We predict that, to first order, the post- emission temperature of EMI+ is a function of the emitted current, assuming an ideal emission process. For a typical emitted current range, we find that the post-emission temperature of EMI+ can vary from 310 to 350 K. At an average ion temperature of 330 K, our theoretical fragmentation model predicts that the mean lifetime of the monomer ranges from 2.1 x 10(-4) ns under an axial electric field of strength 0.1 V/& Aring; to 5.0 x 10(5) ns in the field-free region. Finally, the monomer fragmentation model is incorporated into the single-emitter n-body model of the plume to assess the effects on the evolution of the ion beam. It is found that there is no monomer fragmentation in the acceleration region for monomer temperatures up to 375 K, while at 550 K, the fraction of dissociated monomers can be up to 10%. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial 4.0International (CC BY-NC) license

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