The electronic structure of the formyl radical HCO

Abstract

Many-body perturbation theory (MBPT) and couple-cluster doubles (CCD) calculation are reported for the formyl radical and for points on the potential energy surface corresponding to decomposition of the radical to hydrogen plus carbon monoxide. The predicted equilibrium structure (rCH=2.1 b, rco=2.245 b, and ϑ=124°) and dissociation energy (De=16.6 kcal mol−1) are in excellent agreement with experimental data. An analysis of the saddle-point region of the hypersurface provides a structure for the activated complex (rCH=3.35 b, rco=2.15 b, ϑ=115°) and predicts the critical energy (E0=18.5 kcal mol−1). Comparison of MBPT and CCD results for the dissociation energy and barrier height shows that equivalent results are obtained. A RRKM prediction of the decomposition rate coefficient for HCO→H+CO is also given.

Calculation of Potential Energy Surfaces for HCO and HNO Using Many-Body Methods

“…Since this information is important for theoretical calculations of dynamical processes, we have extended our previous studies to include the angular dependence. For completeness, we also review the results of our dissociation-energy and molecular-structure predictions, 3 and we compare them with experimental and other theoretical values.…”

“…Ab initio UHF calculations for the round electronic state have been used to predict vibrational force constants 3 and to predict hyperfine coupling constants. for the ground state and several low-lying excited states have been reported, along with SCF calculations of potential nergy curves for hydrogen bending and hydrogen dissociation of the radical.…”

“…3 8 A 6-31G** basis set was employed in these calculations. 3 9 The structural parameters for the triatomics have been optimized relative to D-MBPT(4) calculations.…”

“…In previous publications we have described the application of the linkeddiagram-based methods, many-body perturbation theory and coupled-cluster double-excitation theory, for the computation of potential energy surfaces, 3 electronic excitation energies,5,6 and molecular properties. 5 Here we report details of potential energy surface features for two species commonly found in flames:…”

“…A less complete description of the formyl radical potential energy surface has appeared previously. 3 Each of the potential energy surfaces to be described in this report pertains to a reaction important in flames.…”