10049-04-4Relevant articles and documents
Absorption and fluorescence of OClO A2A2-X2B1 in solid Ne, Ar, and Kr. I. Vibrationally unrelaxed A→X emission
Liu, Chin-Ping,Lai, Lih-Huey,Lee, Ying-Yu,Hung, Shao-Ching,Lee, Yuan-Pern
, p. 978 - 987 (1998)
Dispersed laser-induced fluorescence of the A2A2→X2B1 transition of OClO in solid Ne in the spectral range 500-770 nm was recorded when the origin at 20991cm-1 was excited. Progressions with spacings near 939 and 446cm-1 are associated with vibrational modes ν1 and ν2 of the X state. A simultaneous fit of both modes yields ω1″=957.1±1.4, ω2″=452.6±0.4, x11″=4.47±0.04, x22″=0.54±0.05, and x12″=4.00±0.05cm-1. When the 101 line of the A-X system at 21699cm-1 was excited, vibrationally unrelaxed emission was observed in the spectral region 480-600 nm. Excitation of the 201 line at 21284cm-1 generated weak vibrationally unrelaxed progressions. The visible absorption spectrum of OClO in solid Ne in the region 415-488 nm was recorded with a Fourier-transform spectrometer, yielding ν00=20991.3, ν1′=707.9, ν2′=292.5, and 2ν3′=887.6cm-1 for the A state. Simultaneous fits considering either only ν1 and ν2 modes or all three modes yield corresponding spectral parameters. Similar experiments were performed with OClO in solid Ar and Kr. Pronounced increases in ν1′ (716.0cm-1 in Ar and 712.5cm-1 in Kr) and ν2′ (302.3cm-1 in Ar and 303.0cm-1 in Kr) and a decrease in ν00 (188cm-1 and 331cm-1 red-shifted, respectively) from that in the gas phase indicate substantial perturbation of the A state in solid Ar and Kr. An absorption continuum underlying the A-X system is attributed to absorption to the 12A1 state above the predissociation barrier. The phonon interaction increases and the threshold of the continuum decreases as the matrix host is altered from Ne to Ar to Kr.
Formation and Decay of (3PJ)O Atoms in the Laser Flash Photolysis of Chlorine Dioxide (OClO) at 308 nm
Colussi, A. J.
, p. 8922 - 8926 (1990)
The primary quantum yields of O(3PJ) and Cl(2P3/2) atoms in the laser flash photolysis of OClO(g) at 308 nm and 298 K and the kinetics of the subsequent oxygen atom decay have been investigated by time-resolved atomic resonance fluorescence measurements.The determined quantum yields are ΦO = 1.02 +/- 0.05 and ΦCl a finite intercept.The rate constant for the bimolecular channel O + OClO -> O2 + ClO (1) has a value of k1 = (1.6 +/- 0.4) * 10-13 cm3 molecule -1s-1.Termolecular reaction rates for O + OClO + Ar -> ClO3 + Ar (2) can be fit with k20 = (1.4 +/- 0.3) * 10-31 cm6 molecule-2s-1 and k2infinite = (3.1 +/- 0.8) * 10-11 cm3 molecule-1 s-1.A value of ΔHf(ClO3) = 55.6 +/- 4 kcal/mol is derived from k20 and unimolecular reaction theory by assuming a collision efficiency of β = 0.76 for argon.
Temperature Dependence and Mechanism of the Reaction between O(3P) and Chlorine Dioxide
Colussi, A. J.,Sander, S. P.,Friedl, R. R.
, p. 4442 - 4445 (1992)
Second-order rate constants for the decay of O(3P) in excess chlorine dioxide, k11, were measured by flash photolysis-atomic resonance fluorescence as a function of total pressure (20-600 Torr argon) and temperature (248 - 312 K).It was found that (1) k11 is pressure dependent with a value kb that is nonzero at zero pressure and (2) both the third order rate constant (dk11/d)=0 = k0 and kb have negative temperature dependences.These results are consistent with an association reaction leading to an intermediate having two decomposition channels:O + OClO ClO3* (1,2); ClO3* + M -> ClO3 + M (3); ClO3* -> ClO + O2* (4), with E02 > E04.The measured k0 values were used in conjunction with Troe's expression for unimolecular decomposition eates in the low-pressure limit to derive a critical energy for ClO3 of 10700 cm-1, which leads to Δ Hf(ClO3) = 51.9 +/- 5 kcal/mol.This is ca. 4 kcal/mol smaller than the value derived in our previous room temperature study of this reaction.
Outer-Sphere Electron-Transfer Reactions Involving the Chlorite/Chlorine Dioxide Couple. Activation Barriers for Bent Triatomic Species
Stabury, David M.,Lednicky, Lynn A.
, p. 2847 - 2853 (1984)
The kinetics of several redox reactions involving the ClO2/ClO2- couple have been determined in aqueous solution by stopped-flow spectrophotometry.ClO2 is reduced by 2+ to produce ClO2- and 3+ with simple bimolecular kinetics (k=2.1E7 M-1 s-1 at 25 deg C, μ=0.1 M (NaCF3SO3)).ClO2- is oxidized by IrCl62- to produce ClO2 and IrCl63-; the rate law is -d ln 2->/dt = k1/(1++>/Ka), with k1=1.06E4 M-1 s-1 and Ka=1.6E-2 M, the acid dissociation constant of HClO2.For the reaction of ClO2- with IrBr62- k1 is 1.86E4 M-1 s-1.Application of the Marcus-Hush cross relationship to these outer-sphere electron-transfer reactions leads to a self-consistent self-exchange rate constant of 1.6E2 M-1 s-1 for the ClO2/ClO2- couple.An explicit equation for the classical contributions of molecular vibrations to the activation free energy of self-exchange reactions of bent triatomic species has been derived.Calculations of these barriers show that both bending and stretching are important in the activation process.With this equation the activation barriers for the ClO2/ClO2-, NO2/NO2-, and SO2/SO2- redox couples have been rationalized.Nuclear tunneling introduces a correction to the classical rate constant by a factor of 79 for the NO2/NO2- couple.
Kinetics and mechanisms of the ozone/bromite and ozone/chlorite reactions
Nicoson, Jeffrey S.,Wang, Lu,Becker, Robert H.,Hartz, Kara E. Huff,Muller, Charles E.,Margerum, Dale W.
, p. 2975 - 2980 (2002)
Ozone reactions with XO2- (X = Cl or Br) are studied by stopped-flow spectroscopy under pseudo-first-order conditions with excess XO2-. The O3/XO2- reactions are first-order in [O3] and [XO2-], with rate constants k1Cl = 8.2(4) × 106 M-1 s-1 and k1Br = 8.9(3) × 104 M-1 s-1 at 25.0 °C and μ = 1.0 M. The proposed rate-determining step is an electron transfer from XO2- to form XO2 and O3-. Subsequent rapid reactions of O3- with general acids produce O2 and OH. The OH radical reacts rapidly with XO2- to form a second XO2 and OH-. In the O3/CIO2- reaction, CIO2 and CIO3- are the final products due to competition between the OH/CIO2- reaction to form CIO2 and the OH/CIO2 reaction to form CIO3-. Unlike CIO2, BrO2 is not a stable product due to its rapid disproportionation to form BrO2- and BrO3-. However, kinetic spectra show that small but observable concentrations of BrO2 form within the dead time of the stopped-flow instrument. Bromine dioxide is a transitory intermediate, and its observed rate of decay is equal to half the rate of the O3/BrO2- reaction. Ion chromatographic analysis shows that O3 and BrO2- react in a 1/1 ratio to form BrO3- as the final product. Variation of k1X values with temperature gives ΔH?Cl = 29(2) kJ mol-1, ΔS?Cl = -14.6(7) J mol-1 K-1, ΔH?Br = 54.9(8) kJ mol-1, and ΔS?Br = 34(3) J mol-1 K-1. The positive ΔS?Br value is attributed to the loss of coordinated H2O from BrO2- upon formation of an [O3BrO2-]? activated complex.
Kinetics and Products of the BrO + ClO Reaction
Poulet, G.,Lancar, I. T.,Laverdet, G.,Bras, G. Le
, p. 278 - 284 (1990)
The overall rate constant of the BrO + ClO reaction has been measured by the discharge flow mass spectrometry method.The value found at 298 K is k1 = (1.13 +/- 0.15) x 10-11 cm3 molecule-1 s-1.Branchi
Fourier Transform Ultraviolet Absorption Spectroscopy of Jet-Cooled OClO
Richard, EriK C.,Wickham-Jones, C. Tom,Vaida, Veronica
, p. 6346 - 6350 (1989)
The jet-cooled A(2A2) (2B1) absorption spectrum of OClO has been measured with an apparatus that combines a high-resolution Fourier transform UV spectrometer with a high-throughput, continuous molecular jet.The results reported here demonstrate the sensitivity of Fourier transform direct absorption techniques to the investigation of the excited-state dynamics of dissociative systems.Structural and dynamical information is obtained from the jet-cooled absorption spectra of the A transition of OClO.Rotational line width broadening due to predissociation is measured in the higher energy bands up to and beyond the Frank-Condon maximum at ca. 28500 cm-1.The resolution and sensitivity of this absorption technique for the study of the electronic spectroscopy of highly reactive molecules are dicussed.
Photodissociation dynamics of OCIO
Davis, H. Floyd,Lee, Yuan T.
, p. 8142 - 8163 (1996)
Photofragment translational energy spectroscopy was used to study the dissociation dynamics of a range of electronically excited OCIO(A 2A2) vibrational states. For all levels studied, corresponding to OCIO(A 2A2←X 2B1) excitation wavelengths between 350 and 475 nm, the dominant product (>96%) was ClO(2Π)+O(3P). We also observed production of Cl+O2 with a quantum yield of up to 3.9±0.8% near 404 nm, decreasing at longer and shorter wavelengths. The branching ratios between the two channels were dependent on the OClO(A 2A2) excited state vibrational mode. The Cl+O2 yield was enhanced slightly by exciting A 2A2 levels having symmetric stretching+bending, but diminished by as much as a factor of 10 for neighboring peaks associated with symmetric stretching+asymmetric stretching. Mode specificity was also observed in the vibrationally state resolved translational energy distributions for the dominant ClO(2Π)+O(3P) channel. The photochemical dynamics of OClO possesses two energy regimes with distinctly different dynamics observed for excitation energies above and below ～3.1 eV (λ～400 nm). At excitation energies below 3.1 eV (λ>400 nm), nearly all energetically accessible ClO vibrational energy levels were populated, and the minor Cl+O2 channel was observed. Although at least 20% of the O2 product is formed in the ground (X 3∑-g) state, most O2 is electronically excited (a 1Δg). At E2A1 and 2B2. Long dissociation time scales and significant parent bending before dissociation led to nearly isotropic polarization angular distributions (β～0). At excitation energies above 3.1 eV (λ2 yield began to decrease sharply, with this channel becoming negligible at λa large fraction of the excess energy was channeled into C1O+O translational energy. The photofragment anisotropy parameter (β) also increased, implying shorter dissociation time scales. The sharp change in the disposal of excess energy into the ClO products, the decrease of Cl+O2 production, and more anisotropic product angular distributions at E>3.1 eV signify the opening of a new ClO+O channel. From our experimental results and recent ab initio calculations, dissociation at wavelengths shorter than 380 nm to ClO+O proceeds via a direct mechanism on the optically prepared A 2A2 surface over a large potential energy barrier. From the ClO(2Π)+O(3P) translational energy distributions, D0(O-ClO) was found to be less than or equal to 59.0±0.2 kcal/mol.
Vibrational mode-specific photochemical reaction dynamics of chlorine dioxide in solution
Fidder, Henk,Tschirschwitz, Frank,Duehr, Oliver,Nibbering, Erik T. J.
, p. 6781 - 6794 (2001)
The excited electronic state of OClO in solution was assessed. It was found that the fate of this state depends on which vibronic state is created. In general, the reaction dynamics scheme of OClO in solution that emerges from the data is far more complex
Short-wavelength photolysis of jet-cooled OClO(2A2 v1>20) →ClO(X2ΠΩ,v,J) + O(3PJ)
Delmdahl, Ralph F.,Parker, David H.,Eppink, Andre T. J. B.
, p. 8339 - 8346 (2001)
Velocity map imaging was used to study the energy partitioning and anisotropy for the ClO (X2Π)+O (3P2) product channel. Very high anisotropy parameters and extreme channeling of available energy were found. This observation indicates a fundamental change of the fragmentation dynamics of OClO near UV absorption band.
