O( 3 P) + CO 2 collisions at hyperthermal energies

Dynamics of nonreactive scattering, oxygen isotope exchange, and oxygen-atom abstraction

Laurence Y. Yeung, Mitchio Okumura, Jianming Zhang, Timothy K. Minton, Jeffrey T. Paci, Amir Karton, Jan M L Martin, Jon P. Camden, George C Schatz

Research output: Contribution to journalArticle

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Abstract

The dynamics of O( 3P) + CO 2 collisions at hyperthermal energies were investigated experimentally and theoretically. Crossed-molecular-beams experiments at «E coll» = 98.8 kcal mol -1 were performed with isotopically labeled 12C 18O 2 to distinguish products of nonreactive scattering from those of reactive scattering. The following product channels were observed: elastic and inelastic scattering ( 16O( 3P) + 12C 18O 2), isotope exchange ( 18O + 16O 12C 18O), and oxygen-atom abstraction ( 18O 16O + 12C 18O). Stationary points on the two lowest triplet potential energy surfaces of the O( 3P) + CO 2 system were characterized at the CCSD(T)/aug-cc-pVTZ level of theory and by means of W4 theory, which represents an approximation to the relativistic basis set limit, full-configuration-interaction (FCI) energy. The calculations predict a planar CO 3(C 2v, 3Ä) intermediate that lies 16.3 kcal mol -1 (W4 FCI excluding zero point energy) above reactants and is approached by a C 2v transition state with energy 24.08 kcal mol -1. Quasi-classical trajectory (QCT) calculations with collision energies in the range 23-150 kcal mol -1 were performed at the B3LYP/6-311G(d) and BMK/6-311G(d) levels. Both reactive channels observed in the experiment were predicted by these calculations. In the isotope exchange reaction, the experimental center-of-mass (c.m.) angular distribution, T(θ c.m.), of the 16O 12C 18O products peaked along the initial CO 2 direction (backward relative to the direction of the reagent O atoms), with a smaller isotropic component. The product translational energy distribution, P(E T), had a relatively low average of «E T» = 35 kcal mol -1, indicating that the 16O 12C 18O products were formed with substantial internal energy. The QCT calculations give c.m. P(E T) and T(θ c.m.) distributions and a relative product yield that agree qualitatively with the experimental results, and the trajectories indicate that exchange occurs through a short-lived CO 3* intermediate. A low yield for the abstraction reaction was seen in both the experiment and the theory. Experimentally, a fast and weak 16O 18O product signal from an abstraction reaction was observed, which could only be detected in the forward direction. A small number of QCT trajectories leading to abstraction were observed to occur primarily via a transient CO 3 intermediate, albeit only at high collision energies (149 kcal mol -1). The oxygen isotope exchange mechanism for CO 2 in collisions with ground state O atoms is a newly discovered pathway through which oxygen isotopes may be cycled in the upper atmosphere, where O( 3P) atoms with hyperthermal translational energies can be generated by photodissociation of O 3 and O 2.

Original languageEnglish
Pages (from-to)64-84
Number of pages21
JournalJournal of Physical Chemistry A
Volume116
Issue number1
DOIs
Publication statusPublished - Jan 12 2012

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Oxygen Isotopes
oxygen isotopes
Carbon Monoxide
oxygen atoms
Ion exchange
Scattering
Oxygen
Atoms
collisions
Trajectories
products
trajectories
center of mass
scattering
energy
Isotopes
configuration interaction
isotopes
Photodissociation
atoms

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

O( 3 P) + CO 2 collisions at hyperthermal energies : Dynamics of nonreactive scattering, oxygen isotope exchange, and oxygen-atom abstraction. / Yeung, Laurence Y.; Okumura, Mitchio; Zhang, Jianming; Minton, Timothy K.; Paci, Jeffrey T.; Karton, Amir; Martin, Jan M L; Camden, Jon P.; Schatz, George C.

In: Journal of Physical Chemistry A, Vol. 116, No. 1, 12.01.2012, p. 64-84.

Research output: Contribution to journalArticle

Yeung, Laurence Y. ; Okumura, Mitchio ; Zhang, Jianming ; Minton, Timothy K. ; Paci, Jeffrey T. ; Karton, Amir ; Martin, Jan M L ; Camden, Jon P. ; Schatz, George C. / O( 3 P) + CO 2 collisions at hyperthermal energies : Dynamics of nonreactive scattering, oxygen isotope exchange, and oxygen-atom abstraction. In: Journal of Physical Chemistry A. 2012 ; Vol. 116, No. 1. pp. 64-84.
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abstract = "The dynamics of O( 3P) + CO 2 collisions at hyperthermal energies were investigated experimentally and theoretically. Crossed-molecular-beams experiments at «E coll» = 98.8 kcal mol -1 were performed with isotopically labeled 12C 18O 2 to distinguish products of nonreactive scattering from those of reactive scattering. The following product channels were observed: elastic and inelastic scattering ( 16O( 3P) + 12C 18O 2), isotope exchange ( 18O + 16O 12C 18O), and oxygen-atom abstraction ( 18O 16O + 12C 18O). Stationary points on the two lowest triplet potential energy surfaces of the O( 3P) + CO 2 system were characterized at the CCSD(T)/aug-cc-pVTZ level of theory and by means of W4 theory, which represents an approximation to the relativistic basis set limit, full-configuration-interaction (FCI) energy. The calculations predict a planar CO 3(C 2v, 3{\"A}) intermediate that lies 16.3 kcal mol -1 (W4 FCI excluding zero point energy) above reactants and is approached by a C 2v transition state with energy 24.08 kcal mol -1. Quasi-classical trajectory (QCT) calculations with collision energies in the range 23-150 kcal mol -1 were performed at the B3LYP/6-311G(d) and BMK/6-311G(d) levels. Both reactive channels observed in the experiment were predicted by these calculations. In the isotope exchange reaction, the experimental center-of-mass (c.m.) angular distribution, T(θ c.m.), of the 16O 12C 18O products peaked along the initial CO 2 direction (backward relative to the direction of the reagent O atoms), with a smaller isotropic component. The product translational energy distribution, P(E T), had a relatively low average of «E T» = 35 kcal mol -1, indicating that the 16O 12C 18O products were formed with substantial internal energy. The QCT calculations give c.m. P(E T) and T(θ c.m.) distributions and a relative product yield that agree qualitatively with the experimental results, and the trajectories indicate that exchange occurs through a short-lived CO 3* intermediate. A low yield for the abstraction reaction was seen in both the experiment and the theory. Experimentally, a fast and weak 16O 18O product signal from an abstraction reaction was observed, which could only be detected in the forward direction. A small number of QCT trajectories leading to abstraction were observed to occur primarily via a transient CO 3 intermediate, albeit only at high collision energies (149 kcal mol -1). The oxygen isotope exchange mechanism for CO 2 in collisions with ground state O atoms is a newly discovered pathway through which oxygen isotopes may be cycled in the upper atmosphere, where O( 3P) atoms with hyperthermal translational energies can be generated by photodissociation of O 3 and O 2.",
author = "Yeung, {Laurence Y.} and Mitchio Okumura and Jianming Zhang and Minton, {Timothy K.} and Paci, {Jeffrey T.} and Amir Karton and Martin, {Jan M L} and Camden, {Jon P.} and Schatz, {George C}",
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T2 - Dynamics of nonreactive scattering, oxygen isotope exchange, and oxygen-atom abstraction

AU - Yeung, Laurence Y.

AU - Okumura, Mitchio

AU - Zhang, Jianming

AU - Minton, Timothy K.

AU - Paci, Jeffrey T.

AU - Karton, Amir

AU - Martin, Jan M L

AU - Camden, Jon P.

AU - Schatz, George C

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N2 - The dynamics of O( 3P) + CO 2 collisions at hyperthermal energies were investigated experimentally and theoretically. Crossed-molecular-beams experiments at «E coll» = 98.8 kcal mol -1 were performed with isotopically labeled 12C 18O 2 to distinguish products of nonreactive scattering from those of reactive scattering. The following product channels were observed: elastic and inelastic scattering ( 16O( 3P) + 12C 18O 2), isotope exchange ( 18O + 16O 12C 18O), and oxygen-atom abstraction ( 18O 16O + 12C 18O). Stationary points on the two lowest triplet potential energy surfaces of the O( 3P) + CO 2 system were characterized at the CCSD(T)/aug-cc-pVTZ level of theory and by means of W4 theory, which represents an approximation to the relativistic basis set limit, full-configuration-interaction (FCI) energy. The calculations predict a planar CO 3(C 2v, 3Ä) intermediate that lies 16.3 kcal mol -1 (W4 FCI excluding zero point energy) above reactants and is approached by a C 2v transition state with energy 24.08 kcal mol -1. Quasi-classical trajectory (QCT) calculations with collision energies in the range 23-150 kcal mol -1 were performed at the B3LYP/6-311G(d) and BMK/6-311G(d) levels. Both reactive channels observed in the experiment were predicted by these calculations. In the isotope exchange reaction, the experimental center-of-mass (c.m.) angular distribution, T(θ c.m.), of the 16O 12C 18O products peaked along the initial CO 2 direction (backward relative to the direction of the reagent O atoms), with a smaller isotropic component. The product translational energy distribution, P(E T), had a relatively low average of «E T» = 35 kcal mol -1, indicating that the 16O 12C 18O products were formed with substantial internal energy. The QCT calculations give c.m. P(E T) and T(θ c.m.) distributions and a relative product yield that agree qualitatively with the experimental results, and the trajectories indicate that exchange occurs through a short-lived CO 3* intermediate. A low yield for the abstraction reaction was seen in both the experiment and the theory. Experimentally, a fast and weak 16O 18O product signal from an abstraction reaction was observed, which could only be detected in the forward direction. A small number of QCT trajectories leading to abstraction were observed to occur primarily via a transient CO 3 intermediate, albeit only at high collision energies (149 kcal mol -1). The oxygen isotope exchange mechanism for CO 2 in collisions with ground state O atoms is a newly discovered pathway through which oxygen isotopes may be cycled in the upper atmosphere, where O( 3P) atoms with hyperthermal translational energies can be generated by photodissociation of O 3 and O 2.

AB - The dynamics of O( 3P) + CO 2 collisions at hyperthermal energies were investigated experimentally and theoretically. Crossed-molecular-beams experiments at «E coll» = 98.8 kcal mol -1 were performed with isotopically labeled 12C 18O 2 to distinguish products of nonreactive scattering from those of reactive scattering. The following product channels were observed: elastic and inelastic scattering ( 16O( 3P) + 12C 18O 2), isotope exchange ( 18O + 16O 12C 18O), and oxygen-atom abstraction ( 18O 16O + 12C 18O). Stationary points on the two lowest triplet potential energy surfaces of the O( 3P) + CO 2 system were characterized at the CCSD(T)/aug-cc-pVTZ level of theory and by means of W4 theory, which represents an approximation to the relativistic basis set limit, full-configuration-interaction (FCI) energy. The calculations predict a planar CO 3(C 2v, 3Ä) intermediate that lies 16.3 kcal mol -1 (W4 FCI excluding zero point energy) above reactants and is approached by a C 2v transition state with energy 24.08 kcal mol -1. Quasi-classical trajectory (QCT) calculations with collision energies in the range 23-150 kcal mol -1 were performed at the B3LYP/6-311G(d) and BMK/6-311G(d) levels. Both reactive channels observed in the experiment were predicted by these calculations. In the isotope exchange reaction, the experimental center-of-mass (c.m.) angular distribution, T(θ c.m.), of the 16O 12C 18O products peaked along the initial CO 2 direction (backward relative to the direction of the reagent O atoms), with a smaller isotropic component. The product translational energy distribution, P(E T), had a relatively low average of «E T» = 35 kcal mol -1, indicating that the 16O 12C 18O products were formed with substantial internal energy. The QCT calculations give c.m. P(E T) and T(θ c.m.) distributions and a relative product yield that agree qualitatively with the experimental results, and the trajectories indicate that exchange occurs through a short-lived CO 3* intermediate. A low yield for the abstraction reaction was seen in both the experiment and the theory. Experimentally, a fast and weak 16O 18O product signal from an abstraction reaction was observed, which could only be detected in the forward direction. A small number of QCT trajectories leading to abstraction were observed to occur primarily via a transient CO 3 intermediate, albeit only at high collision energies (149 kcal mol -1). The oxygen isotope exchange mechanism for CO 2 in collisions with ground state O atoms is a newly discovered pathway through which oxygen isotopes may be cycled in the upper atmosphere, where O( 3P) atoms with hyperthermal translational energies can be generated by photodissociation of O 3 and O 2.

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