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The “Non‐Reaction” of Ground‐State Triplet Carbon Atoms with Water Revisited
Author(s) -
Schreiner Peter R.,
Reisenauer H. Peter
Publication year - 2006
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200500555
Subject(s) - singlet state , chemistry , intersystem crossing , matrix isolation , triplet state , atomic carbon , ground state , dissociation (chemistry) , photochemistry , carbon fibers , carbene , reactivity (psychology) , atomic physics , molecule , excited state , materials science , analytical chemistry (journal) , medicine , biochemistry , physics , alternative medicine , organic chemistry , chromatography , pathology , composite number , composite material , catalysis
10.1002/cphc.200500555.abs We introduce a novel experimental setup for the generation of carbon atoms by means of pulsed laser ablation with a pulse rate optimized to avoid warming of the matrix. The combination of this technique with annealing of the matrix, recooling, and spectral recording (e.g. IR) allowed us to differentiate between the reactivity of triplet and singlet carbon atoms towards water under matrix‐isolation conditions. Our experimental procedure assures the relaxation of all unreacted carbon atoms to their triplet ground state in the 10 K matrix before spectral recording. In agreement with CCSD(T)/cc‐pVTZ+ZPVE computational data and earlier lower level results, we find that triplet carbon atoms indeed do not react with water, despite their high initial energy. Intersystem crossing of the triplet to singlet states of hydroxy carbene are less important, as the barriers for rearrangement of the initial complex of triplet carbon atoms and water to covalently bound species are too high, and dissociation is more likely. We found no evidence for a direct OH bond‐insertion path for triplet carbon atoms. Self‐condensation reactions of triplet carbon atoms are clearly favored and yield carbon clusters that show reactivity of their own. The proposed formation of aldoses in extraterrestrial environments can therefore only derive from “hot” carbon atoms or through photoreactions.