Crossed-beams and theoretical studies of hyperthermal reactions of O( 3P) with HCl and H2O

Jianming Zhang, Amy L. Brunsvold, Hari P. Upadhyaya, Timothy K. Minton, Jon P. Camden, Jeffrey T. Paci, George C Schatz

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The reactions of O(3P) with HCl and H2O at hyperthermal collision energies (45 - 116 kcal mol-1) have been investigated with crossed-molecular beams experiments and direct dynamics quasiclassical trajectory calculations. Both reactive systems may proceed by two analogous primary pathways, (1) H-atom abstraction to produce OH and either Cl or OH and (2) H-atom elimination to produce H and either ClO or HO2. The H-atom elimination reactions are highly endoergic, and they have been observed experimentally for the first time. The H-atom abstraction reaction follows a stripping mechanism, in which the reagent O atom approaches the target molecule at large impact parameters and the OH product is scattered in the forward direction with respect to the initial direction of the reagent O atom. The H-atom elimination reaction requires low impact parameter collisions. The excitation function for ClO or HO2 increases from threshold to a maximum around 115 kcal mol-1 and then begins to decrease when the product can be formed with sufficient internal energy to undergo secondary dissociation. At collision energies slightly above threshold for H-atom elimination, the ClO or HO2 product scatters primarily in the backward direction, but as the collision energy increases, the fraction of these products that scatter in the forward and sideways directions increases. The dependence of the angular distribution of ClO or HO2 on collision energy is a result of the fact that only certain trajectories, where an H atom on the target molecule is oriented toward the incoming reagent O atom, can release enough energy in translation to lead to stable ClO or HO2 at higher collision energies. These trajectories lead to forward and sideways scattering of ClO or HO2. Moreover, these trajectories do not follow the minimum path and involve larger translational energy release. Therefore, they become dominant at higher collision energies because they lead to lower internal energies and more stable ClO or HO2 products. The energy barrier for the O(3P) + H2O → HO2 + H reaction was determined experimentally to be 60 ± 2 kcal mol -1. Theory predicts that the H-atom abstraction and elimination reactions have comparable cross sections for hyperthermal O(3P) + HCl collisions but that H-atom elimination is only about 20 percent as probable as H-atom abstraction for hyperthermal O(3P) + H2O collisions.

Original languageEnglish
Title of host publicationAIP Conference Proceedings
Pages1275-1280
Number of pages6
Volume1333
EditionPART 1
DOIs
Publication statusPublished - 2011
Event27th International Symposium on Rarefied Gas Dynamics, RGD27 - Pacific Grove, CA, United States
Duration: Jul 10 2011Jul 15 2011

Other

Other27th International Symposium on Rarefied Gas Dynamics, RGD27
CountryUnited States
CityPacific Grove, CA
Period7/10/117/15/11

Fingerprint

atoms
elimination
collisions
trajectories
reagents
energy
products
internal energy
collision parameters
thresholds
forward scattering
stripping
molecular beams
molecules
angular distribution
dissociation
cross sections
scattering
excitation

Keywords

  • Crossed beams
  • H-atom abstraction
  • H-atom elimination
  • HO
  • HCl
  • Hyperthemal atomic oxygen

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Zhang, J., Brunsvold, A. L., Upadhyaya, H. P., Minton, T. K., Camden, J. P., Paci, J. T., & Schatz, G. C. (2011). Crossed-beams and theoretical studies of hyperthermal reactions of O( 3P) with HCl and H2O. In AIP Conference Proceedings (PART 1 ed., Vol. 1333, pp. 1275-1280) https://doi.org/10.1063/1.3562819

Crossed-beams and theoretical studies of hyperthermal reactions of O( 3P) with HCl and H2O. / Zhang, Jianming; Brunsvold, Amy L.; Upadhyaya, Hari P.; Minton, Timothy K.; Camden, Jon P.; Paci, Jeffrey T.; Schatz, George C.

AIP Conference Proceedings. Vol. 1333 PART 1. ed. 2011. p. 1275-1280.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Zhang, J, Brunsvold, AL, Upadhyaya, HP, Minton, TK, Camden, JP, Paci, JT & Schatz, GC 2011, Crossed-beams and theoretical studies of hyperthermal reactions of O( 3P) with HCl and H2O. in AIP Conference Proceedings. PART 1 edn, vol. 1333, pp. 1275-1280, 27th International Symposium on Rarefied Gas Dynamics, RGD27, Pacific Grove, CA, United States, 7/10/11. https://doi.org/10.1063/1.3562819
Zhang J, Brunsvold AL, Upadhyaya HP, Minton TK, Camden JP, Paci JT et al. Crossed-beams and theoretical studies of hyperthermal reactions of O( 3P) with HCl and H2O. In AIP Conference Proceedings. PART 1 ed. Vol. 1333. 2011. p. 1275-1280 https://doi.org/10.1063/1.3562819
Zhang, Jianming ; Brunsvold, Amy L. ; Upadhyaya, Hari P. ; Minton, Timothy K. ; Camden, Jon P. ; Paci, Jeffrey T. ; Schatz, George C. / Crossed-beams and theoretical studies of hyperthermal reactions of O( 3P) with HCl and H2O. AIP Conference Proceedings. Vol. 1333 PART 1. ed. 2011. pp. 1275-1280
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N2 - The reactions of O(3P) with HCl and H2O at hyperthermal collision energies (45 - 116 kcal mol-1) have been investigated with crossed-molecular beams experiments and direct dynamics quasiclassical trajectory calculations. Both reactive systems may proceed by two analogous primary pathways, (1) H-atom abstraction to produce OH and either Cl or OH and (2) H-atom elimination to produce H and either ClO or HO2. The H-atom elimination reactions are highly endoergic, and they have been observed experimentally for the first time. The H-atom abstraction reaction follows a stripping mechanism, in which the reagent O atom approaches the target molecule at large impact parameters and the OH product is scattered in the forward direction with respect to the initial direction of the reagent O atom. The H-atom elimination reaction requires low impact parameter collisions. The excitation function for ClO or HO2 increases from threshold to a maximum around 115 kcal mol-1 and then begins to decrease when the product can be formed with sufficient internal energy to undergo secondary dissociation. At collision energies slightly above threshold for H-atom elimination, the ClO or HO2 product scatters primarily in the backward direction, but as the collision energy increases, the fraction of these products that scatter in the forward and sideways directions increases. The dependence of the angular distribution of ClO or HO2 on collision energy is a result of the fact that only certain trajectories, where an H atom on the target molecule is oriented toward the incoming reagent O atom, can release enough energy in translation to lead to stable ClO or HO2 at higher collision energies. These trajectories lead to forward and sideways scattering of ClO or HO2. Moreover, these trajectories do not follow the minimum path and involve larger translational energy release. Therefore, they become dominant at higher collision energies because they lead to lower internal energies and more stable ClO or HO2 products. The energy barrier for the O(3P) + H2O → HO2 + H reaction was determined experimentally to be 60 ± 2 kcal mol -1. Theory predicts that the H-atom abstraction and elimination reactions have comparable cross sections for hyperthermal O(3P) + HCl collisions but that H-atom elimination is only about 20 percent as probable as H-atom abstraction for hyperthermal O(3P) + H2O collisions.

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KW - HO

KW - HCl

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