Development of the Time-Independent Methods for the Cl + H₂/F + HD Reaction Using Hyper-Spherical Coordinates Including (Full) Spin–Orbit Characteristics

Journal of Chemical Theory and Computation · 2024-05-01 · 2 citations

Recently, a combined study of high-resolution molecular crossed beam experiment and accurate full-dimensional time-dependent theory, including full spin–orbit characteristics on the effect of electronic spin and orbital angular momenta in the F + HD reaction, was reported by some of us, focusing on the partial wave resonance phenomenon (Science 2021, 371, 936–940). It revealed that the time-dependent theory could explain all of the details observed in the high-resolution experiment. Here, we develop two time-independent close-coupling methods using hyperspherical coordinates, including the two-state model, where only a part of the spin–orbit characteristics is considered, and the six-state model, where the full spin–orbit characteristics is considered. With these two newly developed theoretical models and the adiabatic theoretical model, the detailed reaction dynamics of the F + HD (v = 0, j = 0) reaction and the Cl + H2 (v = 0, j = 0) reaction are investigated and compared. Some of the results are compared with the time-dependent quantum wave packet theory and the experimental observations, and good agreements have been obtained, which suggests the validity of the pure-procession approximation in the six-state model using different theoretical methods. This work demonstrates the ability of the reactive scattering theory including full spin–orbit characteristics for describing the reactions of a halogen atom plus hydrogen molecule and its isotopologues.

Hibridon: A program suite for time-independent non-reactive quantum scattering calculations

Computer Physics Communications · 2023 · 26 citations

• Physics
• Quantum mechanics
• Atomic physics

Rotational energy transfer kinetics of optically centrifuged CO molecules investigated through transient IR spectroscopy and master equation simulations

Faraday Discussions · 2022 · 11 citations

• Atomic physics
• Chemistry
• Molecular physics

-dependence than predicted by the model. The results are discussed in terms of angular momentum and energy conservation, and compared to the observed orientational anisotropy decay kinetics of optically centrifuged CO molecules. Models for rotational energy transfer could be improved by including angular momentum effects.

Energy-Dependence of SO 2 Photodissociation with λ=212-220 nm: Transient IR Spectroscopy of Spin-Resolved SO Product States and Ab Initio Calculations

Bulletin of the American Physical Society · 2021-03-18

Nascent Rotational Distributions of CO Excited by Optical Centrifuge and Master Equation Modeling of Collisional Energy Transfer

Frontiers in Optics + Laser Science 2021 · 2021-01-01

Collision relaxation of optically centrifuged CO ( J = 29−80) was modeled using master equation analysis and numerical solution. State-to-state rate constants were determined with an energy gap model and compared to transient state-resolved absorption data.

The excitation of OH by H2 revisited – II. Hyperfine resolved rate coefficients

Monthly Notices of the Royal Astronomical Society · 2020 · 15 citations

• Physics
• Atomic physics
• Astrophysics

ABSTRACT Observations of hyperfine resolved transitions of the hydroxyl radical (OH) are unique probes of the physical conditions in molecular clouds. In particular, hyperfine intensities can be used as an effective thermometer over a wide range of molecular densities. Accurate modelling of the OH emission spectra requires the calculation of collisional rate coefficients for the excitation of OH by H2, the most abundant collisional partner in the molecular clouds. Here, we determine hyperfine resolved rate coefficients for the excitation of OH by H2 using a recently developed highly accurate potential energy surface. State-to-state rate coefficients between the lower hyperfine levels were calculated using recoupling techniques for temperature ranging from 10 to 150 K. Significant differences were found with the earlier values currently used in astrophysical models, the new rate coefficients being larger than the previous ones. Finally, we compute the excitation of the OH radical in cold molecular clouds and star-forming regions. The new rate coefficients were found to increase the hyperfine intensities by a factor of ∼1–2. Consequently, we recommend using this new set of data in any astrophysical model of OH excitation.

Accurate characterization of the lowest triplet potential energy surface of SO2 with a coupled cluster method

The Journal of Chemical Physics · 2019-04-09 · 3 citations

The near-equilibrium potential energy surface (PES) of the ã 3B1 state of SO2 is developed from explicitly correlated spin-unrestricted coupled cluster calculations with single, double, and perturbative triple excitations with an augmented triple-zeta correlation-consistent basis set. The lowest-lying ro-vibrational energy levels of several sulfur isotopologues have been determined using this PES. It is shown that the new ab initio PES provides a much better description of the low-lying vibrational states than a previous PES determined at the multi-reference configuration interaction level. In particular, the theory-experiment agreement for the three lowest-lying vibrational transitions is within 1–3 cm−1.

Enhanced reactivity of fluorine with para-hydrogen in cold interstellar clouds by resonance-induced quantum tunnelling

Nature Chemistry · 2019-06-24 · 60 citations

Applications of Quantum Statistical Methods to the Treatment of Collisions

Advances in chemical physics · 2018-05-08 · 2 citations

This chapter outlines the application of quantum statistical theory to nominally nonreactive collisions that access potential energy surfaces (PESs) having one or more deep wells. It uses the quantum statistical method to calculate transport cross sections, which are weighted averages of differential cross sections. The availability of these PESs allows calculation of cross sections and rate constants for OH + H inelastic collisions, as well as treatment of the O(1D) + H2 reaction. The treatment of the scattering with inclusion of all four PESs and the open-shell nature of the OH and H collision partners is considerably more complex than in the single-PES calculations. The chapter describes the application of the quantum statistical method for the calculation of cross sections and rate constants for various processes involving collisions of the OH radical with hydrogen atoms. Accurate close-coupling calculations based on state-of-the-art PESs provide a way to extend these measurements.

Experimental and theoretical investigation of the temperature dependent electronic quenching of O(1<i>D</i>) atoms in collisions with Kr

The Journal of Chemical Physics · 2018-03-27 · 14 citations

The kinetics and dynamics of the collisional electronic quenching of O(1D) atoms by Kr have been investigated in a joint experimental and theoretical study. The kinetics of quenching were measured over the temperature range 50–296 K using the Laval nozzle method. O(1D) atoms were prepared by 266 nm photolysis of ozone, and the decay of the O(1D) concentration was monitored through vacuum ultraviolet fluorescence at 115.215 nm, from which the rate constant was determined. To interpret the experiments, a quantum close-coupling treatment of the quenching transition from the 1D state to the 3Pj fine-structure levels in collisions with Kr, and also Ar and Xe, was carried out. The relevant potential energy curves and spin-orbit coupling matrix elements were obtained in electronic structure calculations. We find reasonable agreement between computed temperature-dependent O(1D)–Rg (Rg = Ar, Kr, Xe) quenching rate constants and the present measurements for Kr and earlier measurements. In particular, the temperature dependence is well described.