S. Wang

Publications (4)1.01 Total impact

• Article: Kinetics of the reactions of atomic chlorine with H2S, D2S, CH3SH, and CD3SD

  J. M. Nicovich, S. Wang, P. H. Wine
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  ABSTRACT: Time-resolved resonance fluorescence detection of atomic chlorine following 266-nm laser flash photolysis of Cl2CO/RSR'/N2 mixtures has been employed to study the kinetics of Cl reactions with H2S(k1), CH3SH(k2), D2S(k3), and CD3SD(k4) as a function of temperature (193–431 K) and pressure (25–600 torr). Arrhenius expressions which describe our results are (units are 10−11 cm3molecule−1s−1; uncertainties are 2σ, precision only) k1 = (3.69 ± 0.33) exp[(208 ± 24)/T], k2 = (11.9 ± 1.7) exp[(151 ± 38)/T], and k3 = (1.93 ± 0.32) exp[(168 ± 42)/T]. The Cl + CD3SD reaction has been studied at 299 K and 396 K; values for k4 at these two temperatures are essentially the same as those measured for k2. Our results are compared with earlier studies and the mechanistic implications of observed negative activation energies and HD kinetic isotope effects are discussed. © 1995 John Wiley & Sons, Inc.
  International Journal of Chemical Kinetics 09/2004; 27(4):359 - 368. · 1.01 Impact Factor
• Article: Kinetic and mechanistic study of the reaction of atomic chlorine with dimethyl sulfide

  R. E. Stickel, J. M. Nicovich, S. Wang, Z. Zhao, P. H. Wine
  04/2002;
• Article: Kinetics and Thermochemistry of the Cl((sup 2)P(sub J)) + C2Cl4 Association Reaction

  J. M. Nicovich, S. Wang, M L McKee, P. H. Wine
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  ABSTRACT: A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the Cl(sup 2)P(sub j) + C2Cl4 association reaction as a function of temperature (231-390 K) and pressure (3-700 Torr) in nitrogen buffer gas. The reaction is found to be in the falloff regime between third and second order over the range of conditions investigated, although the second-order limit is approached at the highest pressures and lowest temperatures. At temperatures below 300 K, the association reaction is found to be irreversible on the experimental time scale of approximately 20 m-s. The kinetic data at T is less than 300 K have been employed to obtain falloff parameters in a convenient format for atmospheric modeling. At temperatures above 330 K, reversible addition is observed, thus allowing equilibrium constants for C2Cl5 formation and dissociation to be determined. Second- and third-law analyses of the equilibrium data lead to the following thermochemical parameters for the association reaction: Delta-H(298) = -18.1 +/- 1.3 kcal/mol, Delta-H(0) = -17.6 +/- 1.3 kcal/mol, and Delta-S(298) = -27.7 +/- 3.0 cal/mol.K. In conjunction with the well-known heats of formation of Cl((sup 2)P(sub j)) and C2Cl4 the above Delta-H values lead to the following heats of formation for C2Cl5, at 298 and 0 K: Delta-H(f,298) = 8.0 +/- 1.3 kcal/mol and Delta-H(f,0) = 8.1 +/- 1.5 kcal/mol. The kinetic and thermochemical parameters reported above are compared with other reported values, and the significance of reported association rate coefficients for understanding tropospheric chlorine chemistry is discussed.
  05/1997;
• Article: Kinetics and Thermochemistry of the Cl(2PJ) + C2Cl4 Association Reaction

  J. M. Nicovich, S. Wang
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  ABSTRACT: A laser flash photolysis−resonance fluorescence technique has been employed to study the kinetics of the Cl(2PJ) + C2Cl4 association reaction as a function of temperature (231−390 K) and pressure (3−700 Torr) in nitrogen buffer gas. The reaction is found to be in the falloff regime between third and second order over the range of conditions investigated, although the second-order limit is approached at the highest pressures and lowest temperatures. At temperatures below 300 K, the association reaction is found to be irreversible on the experimental time scale of 20 ms. The kinetic data at T < 300 K have been employed to obtain falloff parameters in a convenient format for atmospheric modeling. At temperatures above 330 K, reversible addition is observed, thus allowing equilibrium constants for C2Cl5 formation and dissociation to be determined. Second- and third-law analyses of the equilibrium data lead to the following thermochemical parameters for the association reaction:  ΔH°298 = −18.1 ± 1.3 kcal mol-1, ΔH°0 = −17.6 ± 1.3 kcal mol-1, and ΔS°298 = −27.7 ± 3.0 cal mol-1 K-1. In conjunction with the well-known heats of formation of Cl(2PJ) and C2Cl4, the above ΔH values lead to the following heats of formation for C2Cl5 at 298 and 0 K:  ΔH°f,298 = 8.0 ± 1.3 kcal mol-1 and ΔH°f,0 = 8.1 ± 1.5 kcal mol-1. The kinetic and thermochemical parameters reported above are compared with other reported values, and the significance of reported association rate coefficients for understanding tropospheric chlorine chemistry is discussed.
  01/1996;