Showing papers in "The Journal of Physical Chemistry in 1978"
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TL;DR: In this paper, temperature-programmed desorption of oxygen from 16 metal oxides was studied and it was shown that the desorbed oxygen was associated with surface defects such as vacancies, edges, and corners.
Abstract: Temperature-programmed desorption of oxygen from 16 metal oxides showed that no significant desorption occurred at 10/sup 0/-560/sup 0/C from V/sub 2/O/sub 5/, MoO/sub 3/, Bi/sub 2/O/sub 3/, WO/sub 3/, and Bi/sub 2/O/sub 3/.2MoO/sub 3/ (Group A); that varying amounts of oxygen, always amounting to a few per cent of surface coverage, desorbed with up to four desorption peaks from the transition metal oxides Cr/sub 2/O/sub 3/, MnO/sub 2/, Fe/sub 2/O/sub 3/, Co/sub 3/O/sub 4/, NiO, and CuO (Group B); and that oxygen desorbed from TiO/sub 2/, ZnO, SnO/sub 2/, Al/sub 2/O/sub 3/, and SiO/sub 2/ only after evacuation at 600/sup 0/C and oxygen treatment near room temperature (Group C). The desorbed oxygen was probably associated with surface defects such as vacancies, edges, and corners. The amount of oxygen desorbed from Group B and C oxides decreased with increasing heat of oxide formation. Adsorption on silica and alumina was probably physisorption. Adsorption of oxygen on Group A oxides was probably followed by migration into the bulk and incorporation into the lattice. On Group C oxides, the O/sub 2/(-1) ion was directly identified by ESR spectroscopy.
232 citations
TL;DR: In this article, the rate constants for the reactions of the acid-base forms of the phosphate radical, as well as those of the sulfate radical, with several inorganic compounds were determined.
Abstract: The phosphate radicals were produced by the reaction of e/sub eq//sup -/ with peroxodiphosphate ions and their spectra and acid-base equilibria were determined. The reaction of OH with phosphate ions was also examined and discrepancies in the literature are discussed. The rate constants for the reactions of the acid-base forms of the phosphate radical, as well as those of the sulfate radical, with several inorganic compounds were determined. These reactions involve either hydrogen abstraction or one-electron oxidation. The radicals formed by H abstraction from H/sub 2/O/sub 2/, HOP/sub 3//sup 2 -/, and H/sub 2/PO/sub 2//sup -/ can reduce peroxodisulfate and peroxodiphosphate efficiently and thus propagate a chain reaction. The rate constants for the abstraction reactions are similar for SO/sub 4//sup -/ and H/sub 2/PO/sub 4/ but slower for HPO/sub 4//sup -/ and PO/sub 4//sup 2 -/. The rate constants for oxidation differ considerably for the different radicals and substrates. From these rates it is concluded that the oxidation capabilities decrease in the order SO/sub 4//sup -/ greater than H/sub 2/PO/sub 4/ greater than HPO/sub 4/ greater than PO/sub 4//sup 2 -/.
TL;DR: In this paper, the authors studied the kinetics of the nitrogen pentoxide catalyzed decomposition of ozone in the dark and with photolytic light absorbed by the NO/sub 3/ radical.
Abstract: The kinetics of the nitrogen pentoxide catalyzed decomposition of ozone were studied in the dark and with photolytic light absorbed by the NO/sub 3/ radical Ultraviolet, visible, or infrared absorption cross sections were measured for N/sub 2/O/sub 5/, HNO/sub 3/, NO/sub 2/ and NO/sub 3/ The equilibrium constant for N/sub 2/O/sub 5/ reversible NO/sub 2/ + NO/sub 3/ was found to be (molecules cm/sup -3/, 298--329 K) K = (84 +- 18) x 10/sup 26/ exp(-(11180 +- 100)/T) The rate constants for several reactions were measured: (cm/sup 3/ molecule/sup -1/s/sup -1/) 2NO/sub 3/ --> 2NO/sub 2/ + O/sub 2/, g = (85 +- 28) x 10/sup -13/ exp(-(2450 +- 100)/T); O + N/sub 2/O/sub 5/ --> product, m less than or equal to 2 x 10/sup -14/; O + NO/sub 3/ --> O/sub 2/ + NO/sub 2/, n = (10 +- 04) x 10/sup -11/ By combining the equilibrium constant K with literature values of Ke and Kf, rate constants for reactions e and f were evaluated: NO/sub 2/ + NO/sub 3/ --> NO + O/sub 2/ + NO/sub 2/, e = (25 +- 05) x 10/sup -14/ exp(-(1230 +- 100)/T); NO + NO/sub 3/ --> 2NO/sub 2/, f =more » (19 +- 04) x 10/sup -11/ at 297 K At 1 atm total pressure, the photolysis of NO/sub 3/ occurs with a primary quantum yield less than one in the red region of the spectrum The solar photolysis constants at 298 K for the two paths of dissociation are consistent with the following values: NO/sub 3/ + hnu --> NO + O/sub 2/, j/sub 1/ = 0040 +- 002 s/sup -1/; NO/sub 3/ + hnu --> NO/sub 2/ + O, j/sub 2/ = 0099 +- 002 s/sup -1/ The average quantum yield for process two was approximately 077 for light with wavelengths between 470 and 610 nm, and that for process one was about 023 between 470 and 610 nm but only 007 in the strong absorption region between 610 and 670 nm The photolysis constants may be larger at lower total pressures Infrared absorption ascribed to NO/sub 3/ is due to N/sub 2/O/sub 5/; previously reported visible cross sections for NO/sub 3/ were found to be about a factor of 4 too low and are corrected here; previously reported ultraviolet cross sections for N/sub 2/O/sub 5/ are reversed slightly« less
TL;DR: In this article, the glass transition temperatures of 55 binary molecular liquid systems have been measured at 20 mol % intervals in 55 binary liquid systems and the results used as a basis for estimating by extrapolations the glass-transition temperatures of many common organic liquids which do not vitrify in the pure state and identifying the various structural features of a molecule which collectively determine the magnitude of its T/sub g/.
Abstract: Glass transition temperatures have been measured at 20 mol % intervals in 55 binary molecular liquid systems and the results used as a basis for (a) estimating by extrapolations the glass transition temperatures of many common organic liquids which do not vitrify in the pure state and thereby (b) identifying the various structural features of a molecule which collectively determine the magnitude of its T/sub g/. In most cases, simple linear composition dependences are observed for T/sub g/. The thermodynamic significance of dT/sub g//dx is discussed. In the case of cyclohexanol T/sub g/ estimated for the liquid exceeds the known value of ''T/sub g/'' for the plastic crystal phase by some 10/sup 0/C. The T/sub g/ estimated for CCl/sub 4/ and CHCl/sub 4/ exceed by large intervals the T/sub g/ values reported for vapor-deposited amorphous phases of these substances. 3 figures, 1 table.
TL;DR: In this paper, the electronic absorption spectra of the cation radicals are compared with the photo-electron spectra for the parent molecules in order to find correlations between the two spectra.
Abstract: Cation radicals of some aromatic hydrocarbons, aliphatic amines, and aromatic amines are produced by ..gamma.. irradiation of frozen glassy solutions using organic halides as the solvent. The electronic absorption spectra of the cation radicals are compared with the photoelectron spectra of the parent molecules in order to find correlations between the two spectra. Complementary aspects of the two types of spectroscopy are discussed.