Reactive quenching of OH A 2Σ+ by O2 and CO: experimental and nonadiabatic theoretical studies of H- and O-atom product channels. | Semantic Scholar (2024)

The results are rationalised in terms of cleavage of the N(2)-O bond being dominant in the latter case, with either a similar O atom production or a specific channel producing almost exclusively NO in low vibrational levels for quenching by CO(2).

Surface-hopping quasiclassical trajectory calculations yielded quenching cross sections and a OH X (2)Π product rotational distribution in good accord with experimental observations.

The isotropic ion images reveal that the NO-O2 system evolves through a long-lived NO3 collision complex prior to formation of products, and the corresponding total kinetic energy release distributions support that O2 collision coproducts are formed primarily in the c1Σu - electronic state with NO.

Inhom*ogeneous line broadening in the zero-field spectrum is modeled with an effective Hamiltonian approach that aims to account for the anisotropic molecule-helium interaction potential that arises as the OH-CO complex is displaced from the center of the droplet.

Experimental studies of the dynamical outcomes following collisional quenching of electronically excited OH A(2)Σ(+) radicals by molecular partners demonstrate that the outcomes reflect the strong coupling in the conical intersection region as the system evolves from the excited electronic state to quenched products.

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observation of a marked propensity for production of Pi(A') Lambda-doublet levels was observed, while both OH X (2)Pi spin-orbit manifolds were equally populated, interpreted as dynamical signatures of the nonadiabatic passage of the OH + H(2)/D(2) system through the seams of conical intersection that couple the excited state and ground state surfaces.

The rotational excitation of the OH X (2)Pi products and branching fraction are found to be dynamical signatures of nonadiabatic passage through the conical intersection region.

Nonadiabatic quantum scattering calculations have been carried out for the reactive and nonreactive quenching of OH(A(2)Sigma(+)) in collisions with molecular H( 2) on two new potential energy surfaces of the 1A' and 2A' states and the theory reveals a high degree of rotational excitation of the quenched OH(X (2)II) products.

The sum of the translational energy distributions for H- and D-atom channels is remarkably similar to that obtained for OH A (2)Σ(+) + H(2), where the two channels cannot be distinguished from one another.

Diabatic modeling of the initial momenta in the dynamical calculations captures the key experimental trends: OD X  (2)Π products released primarily in their ground vibrational state with extensive rotational excitation and a branching ratio that strongly favors reactive quenching.

The branching fraction into OH X(2)Pi products states reveals that nonreactive quenching is a significant decay pathway for both systems, accounting for at least 40(1)% of the quenched products with O( 2) and 64(5)% with CO(2).

A steep gradient away from the OH-H2 conical intersection as a function of both the OH orientation and interfragment distance is revealed, which will give rise to a high degree of OH rotational excitation, as observed for the quenched OH X 2Pi products.

F fourier transform spectroscopy is used which is capable of giving more precise values for the relative vibrational populations at low intensities, by recording emission down to lower background pressures (1 x 10(-4) Torr), and by treating the vessel walls so as to remove OHdagger more effectively.

The branching between the product channels provides a new dynamical signature of the conical intersection region(s) that couple the excited state potential for OH A 2Sigma++H2 with OH X 2Pi+H2 and H2O+H products.

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