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Abstract The formation of complex organic molecules by simulated secondary electrons generated in the track of galactic cosmic rays was investigated in interstellar ice analogs composed of methanol and carbon dioxide. The processed ices were subjected to temperature-programmed desorption to mimic the transition of a cold molecular cloud to a warmer star-forming region. Reaction products were detected as they sublime using photoionization reflectron time-of-flight mass spectrometry. By employing isotopic labeling, tunable photoionization and computed adiabatic ionization energies isomers of C2H4O3were investigated. Product molecules carbonic acid monomethyl ester (CH3OCOOH) and glycolic acid (HOCH2COOH) were identified. The abundance of the reactants detected in analog interstellar ices and the low irradiation dose necessary to form these products indicates that these molecules are exemplary candidates for interstellar detection. Molecules sharing a tautomeric relationship with glycolic acid, dihydroxyacetaldehyde ((OH)2CCHO), and the enol ethenetriol (HOCHC(OH)2), were not found to form despite ices being subjected to conditions that have successfully produced tautomerization in other ice analog systems.
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La[N(SiMe 3 ) 2 ] 3 -Catalyzed Ester Reductions with Pinacolborane: Scope and Mechanism of Ester Cleavage
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Exciton dynamics o perovskite nanoclusters has been investigated or the rst time using emtosecond transient absorption (TA) and time-resolved photoluminescence (TRPL) spectroscopy. The TA results show two photoinduced absorption signals at 420 and 461 nm and a photoinduced bleach (PB) signal at 448 nm. The analysis o the PB recovery kinetic decay and kinetic model uncovered multiple processes contributing to electron−hole recombination. The ast component (∼8 ps) is attributed to vibrational relaxation within the initial excited state, and the medium component (∼60 ps) is attributed to shallow carrier trapping. The slow component is attributed to deep carrier trapping rom the initial conduction band edge (∼666 ps) and the shallow trap state (∼40 ps). The TRPL reveals longer time dynamics, with modeled lietimes o 6.6 and 93 ns attributed to recombination through the deep trap state and direct band edge recombination, respectively. The signicant role o exciton trapping processes in the dynamics indicates that these highly conned nanoclusters have deect-rich suraces.more » « less
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acscatal.9b02605
