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Creators/Authors contains: "Signorell, Ruth"

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  1. ; ; ; ; ; ; (, Science)
    Urea is a key molecule in the search for the origin of life and a basic chemical produced in large quantities by industry. Its formation from ammonia and carbon dioxide requires either high pressures and temperatures or, under milder conditions, catalysts or additional reagents. In this study, we observed the spontaneous formation of urea under ambient conditions from ammonia and carbon dioxide in the surface layer of aqueous droplets. Single, optically trapped droplets were probed by using Raman bands as markers. We found the surface layer to act like a microscopic flow reactor, with chemical gradients providing access to unconventional reaction pathways. This observation revealed a general mechanistic scheme for distinctive droplet chemistry. Interfacial chemistry is a possible nonenergetic route for urea formation under prebiotic conditions. 
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    Free, publicly-accessible full text available June 26, 2026
  2. ; ; ; ; ; ; (, Science)
    Low-energy electrons dissolved in liquid ammonia or aqueous media are powerful reducing agents that promote challenging reduction reactions, but can also cause radiation damage to biological tissue. Knowledge of the underlying mechanistic processes remains incomplete, in particular with respect to the details and energetics of the electron transfer steps. Here, we show how ultraviolet (UV) photoexcitation of metal-ammonia clusters could be used to generate tunable low-energy electrons in situ. Specifically, we identified UV light-induced generation of spin-paired solvated dielectrons and their subsequent relaxation by an unconventional electron-transfer-mediated decay as an efficient low-energy electron source. The process is robust and straightforward to induce, with the prospect of improving our understanding of radiation damage and fostering mechanistic studies of solvated electron reduction reactions. 
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  3. ; ; ; ; ; ; (, Physical Chemistry Chemical Physics)
    Abundance spectra of (CO 2 ) N clusters up to N ≈ 500 acquired under a wide range of adiabatic expansion conditions are analyzed within the evaporative ensemble framework. The analysis reveals that the cluster stability functions display a strikingly universal pattern for all expansion conditions. These patterns reflect the inherent properties of individual clusters. From this analysis the size-dependent cluster binding energies are determined, shell and subshell closing sizes are identified, and cuboctahedral packing ordering for sizes above N ≈ 130 is confirmed. It is demonstrated that a few percent variation in the dissociation energies translates into significant abundance variations, especially for the larger clusters. 
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  4. ; ; ; ; ; ; ; ; ; ; et al (, The Journal of Physical Chemistry Letters)