J. V. Michael

Bio: J. V. Michael is an academic researcher from Goddard Space Flight Center. The author has contributed to research in topics: Reaction rate constant & Flash photolysis. The author has an hindex of 16, co-authored 31 publications receiving 668 citations.

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 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.

Selected rate constants for H, O, N, and Cl atoms with substrates at room temperatures

Abstract: Rate constants for H + Cl 2 , H + CH 3 CHO, H + C 3 H 4 , O + C 3 H 6 , O + CH 3 CHO, and Cl + CH 4 have been measured at room temperature by the discharge flow—resonance fluorescence technique. The results are (1.6 ± 0.1) × 10 −11 , (9.8 ± 0.8) × 10 −14 , (6.3 ± 0.4) × 10 −13) (2.00 torr He), (3.95 ± 0.41) × 10 −12 , (4.9 ± 0.5) × 10|su−13 and (1.08 ± 0.07) × 10 −13 , respectively, all in units of cm 3 molecule −1 s −1 . Also N atom reactions with C 2 H 2 , C 2 H 4 , C 3 H 4 , and C 3 H 6 were studied but in no case was there an appreciable rate constant. These results are compared to previous studies.

Absolute rate of the reaction of atomic hydrogen with ethylene from 198 to 320 K at high pressure

Abstract: The rate constant for the H+C2H4 reaction has been measured as a function of temperature. Experiments were performed with high pressures of Ar heat bath gas at seven temperatures from 198 to 320 K with the flash photolysis–resonance fluorescence (FP–RF) technique. Pressures were chosen so as to isolate the addition rate constant k1. The results are well represented by the Arrhenius expression k1= (3.67±0.66) ×10−11 exp(−1040±42/T) cm3 molecule−1 s−1 (quoted errors are two standard deviations). The results are compared with other studies and are theoretically discussed.

Absolute rate of the reaction of Cl(2P) with methane from 200–500 K

Abstract: Rate constants for the reaction of atomic chlorine with methane have been measured from 200-500K using the flash photolysis-resonance fluorescence technique. When the results from fourteen equally spaced experimental determinations are plotted in Arrhenius form a definite curvature is noted. The results are compared to previous work and are theoretically discussed.

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...

Modeling nitrogen chemistry in combustion

Abstract: Understanding of the chemical processes that govern formation and destruction of nitrogen oxides (NOx) in combustion processes continues to be a challenge. Even though this area has been the subject of extensive research over the last four decades, there are still unresolved issues that may limit the accuracy of engineering calculations and thereby the potential of primary measures for NOx control. In this review our current understanding of the mechanisms that are responsible for combustion-generated nitrogen-containing air pollutants is discussed. The thermochemistry of the relevant nitrogen compounds is updated, using the Active Thermochemical Tables (ATcT) approach. Rate parameters for the key gas-phase reactions of the nitrogen species are surveyed, based on available information from experiments and high-level theory. The mechanisms for thermal and prompt-NO, for fuel-NO, and NO formation via NNH or N2O are discussed, along with the chemistry of NO removal processes such as reburning and Selective Non-Catalytic Reduction of NO. Each subset of the mechanism is evaluated against experimental data and the accuracy of modeling predictions is discussed.

Rate Coefficients in the C/H/O System

Abstract: This chapter is a critical survey of reaction rate coefficient data important in describing high-temperature combustion of H2, CO, and small hydrocarbons up to C4. A recommended reaction mechanism and rate coefficient set is presented. The approximate temperature range for this mechanism is from 1200 to 2500 K, which therefore excludes detailed consideration of cool flames, low-temperature ignition, or reactions of organic peroxides or peroxy radicals. Low-temperature rate-coefficient data are presented, however, when they contribute to defining or understanding high-temperature rate coefficients. Because our current knowledge of reaction kinetics is incomplete, this mechanism is inadequate for very fuel-rich conditions (see Warnatz et al., 1982). For the most part, reactions are considered only when their rates may be important for modeling combustion processes. This criterion eliminates considering many reactions among minor species present at concentrations so low that reactions of these species cannot play an essential part in combustion processes. The philosophy in evaluating the rate-coefficient data was to be selective rather than exhaustive: Recent results obtained with experimental methods capable of measuring isolated elementary reaction rate parameters directly were preferred, while results obtained using computer simulations of complex reacting systems were considered only when sensitivity to a particular elementary reaction was demonstrated or when direct measurements are not available. Theoretical results were not considered.

A KInetic Database for Astrochemistry (KIDA)

Abstract: We present a novel chemical database for gas-phase astrochemistry. Named the KInetic Database for Astrochemistry (KIDA), this database consists of gas-phase reactions with rate coefficients and uncertainties that will be vetted to the greatest extent possible. Submissions of measured and calculated rate coefficients are welcome, and will be studied by experts before inclusion into the database. Besides providing kinetic information for the interstellar medium, KIDA is planned to contain such data for planetary atmospheres and for circumstellar envelopes. Each year, a subset of the reactions in the database (kida.uva) will be provided as a network for the simulation of the chemistry of dense interstellar clouds with temperatures between 10 K and 300 K. We also provide a code, named Nahoon, to study the time-dependent gas-phase chemistry of zero-dimensional and one-dimensional interstellar sources.

Kinetic modeling and sensitivity analysis of nitrogen oxide formation in well-stirred reactors

Abstract: We have modeled the experimental data of Bartok et al. and Duterque et al. on methane combustion in stirred reactors. A method to calculate the first-order sensitivities of the mole fractions and temperature with respect to the rate constants is discussed and applied to nitric oxide production. We have thus been able to evaluate the nitrogen chemistry in the presence of hydrocarbons under stirred conditions. We find the extended Zeldovich mechanism to be the major source of NO under lean conditions, while the prompt-NO formation is dominant under fuel-rich conditions. The important features of the model under fuel-rich conditions are the following: 1. 1. The reaction CH + N2 ⇄ HCN + N is the only important initiating step in the prompt-NO formation. 2. 2. The CH concentration is established through the sequence CH 3 + ⇄ CH 2 + HX , CH 2 + ⇄ CH + HX , CH 2 + X ⇄ C + OH , where X is H or OH. 3. 3. Nitric oxide is recycled back to CN and HCN through reactions with C, CH, and CH2. This results in the exhaust of significant quantities of HCN from the reactor.