A simplified multiple-well approach for the master equation modeling of blackbody infrared radiative dissociation (BIRD) of hydrated carbonate radical anions Magdalena Salzburger , Milan Ončák, Christianvan der Linde, Martin Klemens Beyer Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Austria ●‑ (H 2 O) 1,2 are found in the lower region of the ionosphere and in the troposphere. Their infrared spectra indicate significant spectral broadening, explained by quantum chemical calculations with a highly fluxional nature of the clusters [1]. In this work, we analyze blackbody infrared radiative dissociation (BIRD) of singly and doubly hydrated carbonate radical anion clusters at different temperatures and perform master equation modeling of these challenging systems. Molecular clusters CO 3 The molecular clusters are generated with a laser vaporisation source and guided to a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer (FT-ICR-MS). The temperature of the ICR cell is controlled by a variable supply of liquid nitrogen or warm water. We observe loss of water from CO 3 ●‑ (H 2 O) 1,2 clusters. BIRD‑kinetics were measured for temperatures between 210 and 350K. Dissociation kinetics are first order, and are fitted with a genetic algorithm to obtain unimolecular rate constants. The kinetics exhibit apparent Arrhenius behavior. Master equation modeling of the temperature dependent kinetics is performed, taking into account all low-lying isomers that are populated at the experimental temperatures. Densities of states calculated with the Beyer-Swinehart algorithm are compared with ab initio molecular dynamics simulations. Modeling yields activation energies for water evaporation, which are compared with quantum chemical calculations of the water binding energy on the CCSD/aug-cc-pVDZ level of theory. References 1. M. G. Münst, M. Ončák, M. K. Beyer, C. van der Linde, J. Chem. Phys. 154, 084301 (2021). DOI: 10.1063/5.0038280
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