Abstract
The statistical model of atom-diatom insertion reactions is combined with coupled-states capture theory to calculate integral cross sections for formation of specific rotational/fine-structure states of the SD product of the title reaction. The four electronic potential energy surfaces that correlate with the products ( and ) and an accurate description of the electronic and spin-orbit couplings between them have been determined from ab initio calculations. The dependence of the cross sections upon the product rotational quantum number shows a statistical behavior similar to that computed with the simple prior statistical model. We predict a significant preference for formation of the lower versus the upper spin-orbit manifold but essentially equal and -doublet populations. The computed SD rotational/fine-structure state distribution is in good agreement with the distribution measured experimentally for this reaction by Khachatrian and Dagdigian [J. Chem. Phys.122, 024303 (2005)]. The calculations predict the : spin-orbit population ratio to be slightly larger than experimentally observed.
This research was supported by the National Science Foundation under Grant No. CHE-0413743.
I. INTRODUCTION
II. MULTISTATE STATISTICAL MODEL
III. AB INITIO POTENTIAL ENERGY SURFACES
IV. RESULTS
A. Computational details
B. SD product state distribution
V. COMPARISON WITH EXPERIMENT AND DISCUSSION
Key Topics
- Hydrogen reactions
- 39.0
- Statistical model calculations
- 21.0
- Manifolds
- 17.0
- Chemical reaction cross sections
- 16.0
- Laser induced chemistry
- 15.0
Figures
Schematic diagram of the reaction path for the reaction. Only the lowest-energy PES is shown in the reactant arrangement.
Schematic diagram of the reaction path for the reaction. Only the lowest-energy PES is shown in the reactant arrangement.
Energy level diagram for the lower rotational/fine-structure levels of . The fine-structure manifolds are labeled and and correspond to and , respectively. For each , there are two -doublet levels, of nominal and reflection symmetry; the energy differences between them are small, and the levels are not separately plotted in the diagram. Since the spin-orbit splitting is much greater than the rotational spacings, follows Hund’s case (a) coupling fairly closely.
Energy level diagram for the lower rotational/fine-structure levels of . The fine-structure manifolds are labeled and and correspond to and , respectively. For each , there are two -doublet levels, of nominal and reflection symmetry; the energy differences between them are small, and the levels are not separately plotted in the diagram. Since the spin-orbit splitting is much greater than the rotational spacings, follows Hund’s case (a) coupling fairly closely.
Contour plots of the SH–H PESs for the (upper panel) and (lower panel) states for a fixed OH internuclear separation . The values of the contours are given in . Note that corresponds to linear SHH.
Contour plots of the SH–H PESs for the (upper panel) and (lower panel) states for a fixed OH internuclear separation . The values of the contours are given in . Note that corresponds to linear SHH.
Contour plots of the SH–H PESs for the (upper panel) and (lower panel) states. See caption to Fig. 3 for details.
Contour plots of the SH–H PESs for the (upper panel) and (lower panel) states. See caption to Fig. 3 for details.
Comparison of reactive cross sections at a collision energy of . The cross sections were obtained from single-PES CS statistical model calculations using the PES presented in the present paper and that of Ho et al. (Ref. 40). Since the open-shell nature of the SH product is not explicitly considered in single-PES calculations, the rotational quantum numbers are integers, designated in conventional spectroscopic notation as .
Comparison of reactive cross sections at a collision energy of . The cross sections were obtained from single-PES CS statistical model calculations using the PES presented in the present paper and that of Ho et al. (Ref. 40). Since the open-shell nature of the SH product is not explicitly considered in single-PES calculations, the rotational quantum numbers are integers, designated in conventional spectroscopic notation as .
Integral cross sections for formation of at a collision energy of for the energetically accessible vibrational levels (upper panel) and (lower panel). The cross sections for formation of SD products in each fine-structure manifold and each -doublet level are shown separately.
Integral cross sections for formation of at a collision energy of for the energetically accessible vibrational levels (upper panel) and (lower panel). The cross sections for formation of SD products in each fine-structure manifold and each -doublet level are shown separately.
Partial cross sections for formation of products in the (solid) and (dashed) -doublet levels, as a function of the product helicity quantum number , at a collision energy of .
Partial cross sections for formation of products in the (solid) and (dashed) -doublet levels, as a function of the product helicity quantum number , at a collision energy of .
Comparison of the rotational fine-structure state distribution of the products from the reaction computed in the present study (open symbols connected with solid lines), at a collision energy of , and that measured experimentally (filled symbols) by Khachatrian and Dagdigian (Ref. 38). The experimental data have been scaled so that their sum equals the sum, over both fine-structure manifolds, of the computed cross sections. The solid and open points present cross sections for formation of the and -doublet levels, respectively.
Comparison of the rotational fine-structure state distribution of the products from the reaction computed in the present study (open symbols connected with solid lines), at a collision energy of , and that measured experimentally (filled symbols) by Khachatrian and Dagdigian (Ref. 38). The experimental data have been scaled so that their sum equals the sum, over both fine-structure manifolds, of the computed cross sections. The solid and open points present cross sections for formation of the and -doublet levels, respectively.
Article metrics loading...
Full text loading...
Commenting has been disabled for this content