- High-resolution spectroscopy of H2SO4, HDSO 4, and D2SO4 vapor in the region 1200-10,000 cm-1
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The high-resolution (0.05 cm-1) spectra of gas-phase H 2SO4, HDSO4, and D2SO4 were measured over the frequency region 1200-10,000 cm-1 using Fourier-transform infrared spectroscopy. The increased resolution of this work compared with previous studies has lead to an improved vibrational analysis of H2SO4. This study has answered unresolved questions about combination bands and overlapping features from previous gas-phase spectroscopic studies of H2SO4 and marks the first experimental measurement of the ν8 and ν15 torsional vibrations in this molecule. This work leads to a brief discussion on vibrational mode mixing in sulfuric acid.
- Hintze,Feierabend,Havey,Vaida
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- The Existence of Tricyanomethane
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Calcium tricyanomethanide reacts with hydrogen fluoride under formation of tricyanomethane and Ca(HF2)2. Tricyanomethane is stable below -40 °C and was characterized by IR, Raman, and NMR spectroscopy. The vibrational spectra were compared to the quantum-chemical frequencies at the PBE1PBE/6-311G(3df,3dp) level of theory and confirm the predicted C3v symmetry of the molecule with regular C-H (109.8pm), C-C (146.7pm), and C-N (114.7pm) bonds.
- Soltner, Theresa,H?usler, Jonas,Kornath, Andreas J.
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- Properties of Crystalline Sulfuric Acid in Ultrahigh Vacuum: Incongruent Melting to the Liquid Azeotrope and Its Slow Recrystallization
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The growth and characterization of ultrathin (ca. 80 monolayers) films of pure, crystalline sulfuric acid and of the liquid H2SO4 + H2O azeotrope in ultrahigh vacuum (UHV) are described.The films, which were deposited on a Pt(111) substrate, were synthesized in vacuo via the reaction of co-condensed mixtures of H2O and SO3.Fourier transform infrared reflection-absorption spectroscopy (FTIRAS) shows that the pure, crystalline acid forms when such mixtures are briefly annealed at 260 K.Crystalline H2SO4 is stable in UHV until 285 K, at which temperature FTIRAS measurements suggest the melting occurs.The melting temperature is equal, within experimental error, to the melting point of a macroscopic sample of crystalline H2SO4.Analysis of the gas phase composition during melting reveals that SO3 is expelled from a film as it melts.The liquid is identified as the azeotrope of H2SO4 and H2O, formed in the incongruent melting of H2SO4.The H2SO4 + H2O mixtures can be supercooled to 255 K.Freezing results in the formation of pure, crystalline H2SO4 and is accompanied by the expulsion of H2O into the gas phase.To our knowledge, this work provides the first observation of melting of a molecular solid under UHV.
- Schindler, Liesl R.,Roberts, Jeffrey T.
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