Comparison of rate constants for reactions of hydrogen atoms with chlorine, fluorine, iodine chloride, and chlorine fluoride

Abstract

The infrared emission intensities from the HC1 and HF products have been used to assign relative rate constants for the reaction of H atoms with Cl2, F2, GIF, and IC1. The experiments were done in a fast flow apparatus utilizing ~1 torr of Ar carrier gas. The vibrational distributions obtained from analysis of the chemiluminescence recorded with a Fourier transform spectrometer at the first window of the flow reactor were very close to the initial distributions produced by the chemical reaction. Except for a small residue of population in the high J levels of HC1 from the H + IC1 reaction, the rotational populations had relaxed to a room temperature Boltzmann distribution. The relative rate constants for HC1 formation from the F2, Cl2, GIF, and IC1 series are 0.053:1.00:1.99:2.42. Since the absolute rate constant is well known for Cl2, these data, plus the vibrational-rotational distributions of product states, give absolute rate constants for formation of individual product quantum states. Summation of the HC1 and HF relative intensities from + GIF gave a macroscopic branching ratio of 5.2 favoring the HC1 channel. For the H + IC1 reaction, the HI/HC1 ratio is <0.5. Dynamical models based upon the data of this and the preceding paper are discussed.

An analytical potential energy surface of the HClF (2A′) system based on ab initio calculations. Variational transition state theory study of the H+ClF→F+HCl, Cl+HF and F+HCl→Cl+HF reactions and their deuterium isotope variants

“…k 3(H) /k 3(D) \ 2.07È1.41 This isotope e †ect can be understood in a similar way as for reactions (1) and (2). Here, the energy barriers (e.g., 0.42 *V a G and 0.59 kcal mol~1 for reaction (3) with H and D respectively, at T \ 0 K) are very important. Transmission coefficients follow an opposite direction (e.g., i 3(H) /i 3(D) \ 0.46È1.00 within the range 150È1000 K) and the mass e †ect is negligible.…”

“…Therefore, the lowest 2A@ PES allows the correlation of all reactants and products of reactions (1), ( 2) and (3). In symmetry, a C =v 2&`PES correlates to the ground state of reactants and products of reactions ( 1) and ( 2), and two PESs (2&`and 2%) correlate for reaction (3). As it has been found that the HCl 2 (2A@) wavefunction is mostly single-determinantal at all the stationary points of the PES,21 the full unrestricted secondorder (UMP2) method is, in principle, accurate MÔllerÈPlesset enough to be used for this study.…”

“…In previous studies on reactions (1) and (2) using infrared chemiluminescence techniques, there have been measured detailed rate constants k(v@) and k(v@, J@) at 300 K.1h3 Microscopic branch-ing has also been observed in reaction (2) but not in reaction (1). Infrared chemiluminescence studies of reaction (3) have also furnished detailed rate constants k(v@) and k(v@, J@) at 300 and 1700 K ;4 k(v \ 0, 1, 2), k(v \ 1, J), k(v@ o v) and other detailed rate constants have also been reported in the same work (primed variables refer to the products vibrational and rotational quantum numbers). Thermal rate constants for the three reactions5h8 and the macroscopic branching ratio k 1 /k 2 at 300 K1h3,9 are also available in the literature.…”

A Review of Recent Experiments and Calculations Relevant to the Kinetics of the HF Laser

“…The only uncertainty concerns the nascent population of vу8. On the low end, the fast flow reactor studies of Setser 22 and Kaufman 23 found no P 8 -P 10 , while on the high end the pressure-pulse chemiluminescence mapping experiments of Tardy 19 found substantial populations for vϭ8 -9. The presence of at least some P 8 -P 10 is supported by the infrared chemiluminescence studies of Polanyi and Jonathan, who reported minor P 8 -P 10 .…”

Spectroscopy and photochemistry of free radicals formed by the reaction of F atoms with small molecules

“…A possible complication in arrested relaxation experiments is the loss of energy from HF by wall collisions. To minimize this perturbation, Setser and co-workers have recently developed a fast flow reactor for HF chemiluminescence studies [8]. Results of observations with this system have been compared with those obtained in arrested relaxation experiments [9], and the fast flow reactor has been used to survey the reactions of F atoms with the Group III, IV, and V hydrides [I0].…”