Walter A. Payne

Bio: Walter A. Payne is an academic researcher from Goddard Space Flight Center. The author has contributed to research in topics: Reaction rate constant & Chemical kinetics. The author has an hindex of 26, co-authored 59 publications receiving 1393 citations.

A flasch photolysis–resonance fluorescence study of the formation of O(1D) in the photolysis of water and the reaction of O(1D) with H2, Ar, and He −

Abstract: The relative importance of two primary processes in the photolyis of water: (1) H2O + h (nu) yields H + OH, and (2) H2O + h (nu) yields H2 + OD-1 were determined in a direct manner by time resolved detection (via resonance fluorescence) of H and O formed in processes 1 and 2 respectively. The initially formed OD-1 was deactivated to ground state OP-3 prior to detection via resonance fluorescence. The relative quantum yields for processes 1 and 2 are 0.89 and 0.11 for the wavelength interval 105 to 145nm and = to or greater than 0.99, and = to or less than 0.01 for the wavelength interval 145 to 185nm. Rate constants at 300 K for the reactions OD-1 + H2, + Ar, and + He are presented.

Absolute rate of the reaction of N(4S) with NO from 196–400 K with DF–RF and FP–RF techniques

Abstract: Rate constants for the reaction of N(4S) with NO have been measured from 196–400 K with two independent techniques both which utilize resonance fluoresence detection for temporal analysis of N(4S). The reaction has been studied at 196, 297, and 370 K by the discharge flow‐resonance fluorescence technique (DF‐RF) and the measured rate constant is best represented by the temperature independent value of (2.7±0.4) ×10−11 cm3 molecule−1 s−1. The technique of flash photolysis‐resonance fluorescence (FP‐RF) has been used to study the reaction at 233, 298, and 400 K, and the results are best represented by the temperature independent value of (4.0±0.2) ×10−11 cm3 molecule−1 s−1. Combination of the results suggests a value of (3.4±0.9) ×10−11 cm3 molecule−1 s−1 between 196–400 K. In this work discrimination between O(3P) atom and N(4S) atom fluorescence was necessary, and this was accomplished by inclusion of an O atom resonance line filtering section as an integral part of the resonance lamp. The suggested value for the rate constant is combined with a statistical mechanical evaluation of the equilibrium constant for N(4S)+NO=N2+O(3P) to give a revised estimate for the rate constant of the back reaction. The back reaction is important in the Zeldovich mechanism for thermal production of NO in combustion systems. The rate constant is also theoretically discussed in terms of collision theory.

Absolute rate constant for the reaction of atomic hydrogen with acetylene over an extended pressure and temperature range

Abstract: The technique of flash photolysis coupled with time resolved detection of H via resonance fluorescence has been used to obtain absolute rate parameters for the reaction of atomic hydrogen with acetylene, i.e., H+C2H2?C2H3* (1); C2H3*+M→C2H3+M (2). The rate constant for the reaction is strongly pressure dependent and was measured over the pressure range 10 to 700 torr. The reaction was also studied as a function of temperature over the range 193 to 400 °K and the high pressure limit of the rate constant at each temperature was used to obtain the Arrhenius expression k1= (9.63±0.60) ×10−12 exp(−2430±30/1.987T) cm3 molecule−1⋅sec−1. The present results are compared with those of previous studies.

Temperature dependence of the reaction of nitrogen atoms with methyl radicals

Abstract: The discharge-flow mass spectrometry technique has been used to measure the kinetics of the reaction N + CH{sub 3} {yields} products over the temperature range 200-423 K. The results are as follows (10{sup {minus}11} cm{sup 3} s{sup {minus}1}): k{sub 1}(200 K) = (6.4 {plus minus} 2.1), k{sub 1}(298 K) = (8.5 {plus minus} 2.0), k{sub 1}(363 K) = (14 {plus minus} 3.0), and k{sub 1}(423 K) = (17 {plus minus} 5.0). Quoted uncertainties include statistical (95% confidence) and systematic (15%) errors. Interpreting the temperature dependence is difficult, as there is a possibility that the reaction behaves in a non-Arrhenius manner. Possible causes of this behavior are discussed, and comparisons are made with reactions showing similar properties. The results of this study have implications regarding the formation of HCN in the atmosphere of Titan.

Absolute rate constants for the reaction of atomic hydrogen with ketene from 298 to 500 K

Abstract: Rate constants for the reaction of atomic hydrogen with ketene have been measured at room temperature by two techniques, flash photolysis-resonance fluorescence and discharge flow-resonance fluorescence. The measured values are (6.19 + or - 1.68) x 10 to the -14th and (7.3 + or - 1.3) x 10 to the -14th cu cm/molecule/s, respectively. In addition, rate constants as a function of temperature have been measured over the range 298-500 K using the FP-RF technique. The results are best represented by the Arrhenius expression k = (1.88 + or - 1.12) x 10 to the -11th exp(-1725 + or - 190/T) cu cm/molecule/s, where the indicated errors are at the two standard deviation level.

Adiabatic connection for kinetics

Abstract: A new hybrid Hartree−Fock−density functional (HF-DF) model called the modified Perdew−Wang 1-parameter model for kinetics (MPW1K) is optimized against a database of 20 forward barrier heights, 20 r...

Plasma-liquid interactions: A review and roadmap

Abstract: Plasma–liquid interactions represent a growing interdisciplinary area of research involving plasma science, fluid dynamics, heat and mass transfer, photolysis, multiphase chemistry and aerosol science. This review provides an assessment of the state-of-the-art of this multidisciplinary area and identifies the key research challenges. The developments in diagnostics, modeling and further extensions of cross section and reaction rate databases that are necessary to address these challenges are discussed. The review focusses on non-equilibrium plasmas.

Fundamentals of atmospheric modeling

Abstract: Preface Acknowledgements 1. Introduction 2. Atmospheric structure, composition and thermodynamics 3. The continuity and thermodynamic energy equations 4. The momentum equation in Cartesian and spherical coordinates 5. Vertical-coordinate conversions 6. Numerical solutions to partial differential equations 7. Finite-differencing the equations of atmospheric dynamics 8. Boundary-layer and surface processes 9. Radiative energy transfer 10. Gas-phase species, chemical reactions and reaction rates 11. Urban, free-tropospheric and stratospheric chemistry 12. Methods of solving chemical ordinary differential equations 13. Particle components, size distributions and size structures 14. Aerosol emission and nucleation 15. Coagulation 16. Condensation, evaporation, deposition and sublimation 17. Chemical equilibrium and dissolution processes 18. Cloud thermodynamics and dynamics 19. Irreversible aqueous chemistry 20. Sedimentation, dry deposition and air-sea exchange 21. Model design, application and testing Appendix A. Conversions and constants Appendix B. Tables References Index.