Alan C. Baldwin

Heterogeneous atmospheric reactions - Sulfuric acid aerosols as tropospheric sinks

The collisional reaction probabilities of several atmospheric species on bulk sulfuric acid surfaces indicate that heterogeneous processes may be important in tropospheric chemistry.

Reactions of methyl radicals of importance in combustion systems

Abstract Methyl radicals have been shown not to undergo a rapid bimolecular reaction with oxygen or nitric oxide at temperatures up to 1220 K.

Infrared multiphoton chemistry: Comparison of theory and experiment, solution of the master equation

An energy-grained master equation was used to model the multiphoton pumping process in SF6. An energy-dependent absorption cross section that was approx. inversely dependent on the level of excitation was needed to reproduce exptl. data on the fraction decompd. per pulse.

IR photochemistry: A unified approach for single‐channel reactions. I. Theory and computational examples

A model for infrared multiphoton decomposition of polyatomic molecules based on an energy‐grained master equation (EGME) shows remarkably uniform behavior over a wide range of physically reasonable model parameters. These parameters encompass the size of the molecule, the reaction threshold energy, the variation of the decomposition rate constant above the threshold, and the functional dependence of the infrared absorption process on the internal energy of the molecule. The results are shown to be uniformly well represented by a cumulative log–normal distribution function for reaction yield versus time or fluence. A complementary approach based on the distribution of first passage times for a Markovian stochastic process in discrete state space and continuous time shows that the yield behavior of the EGME can be conveniently calculated without solution of the full set of equations. The uniform behavior of the model results yields a powerful method for presenting and analyzing experimental data.

Collisional energy transfer from excited polyatomic molecules produced by infrared multiple photon absorption

A simple energy‐grained master equation is used to model data on the multiphoton dissociation of CF2HCl as a function of laser fluence and argon bath–gas pressure. Information on energy transfer from vibrationally excited CF2HCl is obtained from an analysis of the competition between laser pumping and collisional energy removal using suitable parametrizations of the laser intensity and the collision process.

IR photochemistry: A unified approach for single‐channel reactions. II. Treatment of experimental data

In the preceding paper of this series [J. Chem. Phys. 74, XXXX (1981)], it was shown that multiphoton decomposition yields versus fluence or time can be expressed as cumulative log–normal distribution functions (CLNDF). In the present paper, this idea is exploited for the purpose of presenting and analyzing experimental data. Such data from several different laboratories are used to show the effects of convolution of the laser spatial profile. Also shown are examples of homogeneous behavior, ’’active /inactive’’ population subsets, and more general cases. This approach permits a unified description of the experimental system, regardless of the potential complexities.

An explanation of the preferential formation of less stable isomers in three-body reactions - Cl + NO2 + M; ClO + NO2 + M

Low‐pressure limit rate constants for the three‐body reactions, (1) Cl+NO2+M→ products and (2) ClO+NO2+M→ products, have been calculated according to Troe’s method [J. Chem. Phys. 66, 4758 (1977)]. The result for the reaction of Cl+NO2+M is in excellent agreement with the experimental finding of Niki et al. [Chem. Phys. Lett. 59, 78 (1978)]. An explanation is proposed to account for apparent discrepancy between the measured rate constants for ClO+NO2+M in the forward and reverse directions. The stratospheric implications are also discussed.

Alkoxy radical reactions: the isomerization of n-butoxy radicals generated from the pyrolysis of n-butyl nitrite

Abstract The very low-pressure pyrolysis of n -butyl nitrite has been studied at temperatures from 590–750 K. Evidence is presented that the n -butoxy radicals so formed undergo a fast intramolecular isomerization.

IR photochemistry: A unified approach for single-channel reactions. A simple approximate solution of the master equation

Abstract A birth and death master equation with simple solutions is used to approximate the complete solution of the full master equation for collisionless multiphoton decomposition. Limits of validity and methods for assigning the effective decomposing level are discussed, giving a simple solution of the full master equation.