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Title: Photodissociation dynamics of superexcited O{sub 2}: Dissociation channels O({sup 5}S) vs. O({sup 3}S)

The photodissociation dynamics of O{sub 2}, O{sub 2} + hυ → O({sup 3}P) + O(2p{sup 3}({sup 4}S)3s, {sup 3}S/{sup 5}S), has been studied by combining the XUV laser pump / UV laser probe and velocity map imaging methods in the photon energy range 14.64–15.20 eV. The fragment yield spectra of O({sup 3}S) and O({sup 5}S) and their velocity map images have been recorded using the state-selective (1+1) REMPI method to detect the fragments. The fragment yield spectra show resolved fine structure that arises from the predissociated Rydberg states I, I{sup ′} and I{sup ″} ({sup 3}Π{sub Ω=0,1,2}). The branching ratios between the two decay channels have been measured by one-photon ionization of the fragments O({sup 3}S) and O({sup 5}S) simultaneously. It is surprising to find that the dissociation cross sections for the production of O({sup 5}S) are larger than, or comparable to, those of O({sup 3}S) for the I and I{sup ′} states, while the cross sections for the production of O({sup 5}S) are smaller than those of O({sup 3}S) for the I{sup ″} state. All fragments O({sup 5}S) arise from perpendicular transitions, which provides direct experimental evidence about the symmetry assignments of the states I, I{sup ′} and I{supmore » ″} excited in this energy region. Although most of the fragments O({sup 3}S) arise from perpendicular transitions, some of them are from parallel transitions. Based on the calculated ab initio potential energy curves, we propose that the neutral dissociation into O({sup 3}P) + O({sup 3}S) occurs mainly via the interaction of the Rydberg states I, I{sup ′}, and I{sup ″} with the vibrational continuum of the diabatic 8{sup 3}Π{sub u} state (1π{sub u}{sup −1}(a{sup 4}Π{sub u})3sσ{sub g},{sup 3}Π{sub u}), while the neutral dissociation into O({sup 3}P) + O({sup 5}S) occurs mainly via the interaction of Rydberg states I, I{sup ′}, and I{sup ″} with the diabatic 7{sup 3}Π{sub u} (1π{sub g}{sup −1}(X{sup 2}Π{sub g})3pσ{sub u},{sup 3}Π{sub u})« less
Authors:
;  [1] ;  [1] ;  [2]
  1. Department of Physics and State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China)
  2. (China)
Publication Date:
OSTI Identifier:
22308747
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 1; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALLOCATIONS; BRANCHING RATIO; CROSS SECTIONS; DISSOCIATION; FINE STRUCTURE; INTERACTIONS; IODINE IONS; LASERS; PHOTOIONIZATION; PHOTOLYSIS; PHOTONS; POTENTIAL ENERGY; RYDBERG STATES; SPECTRA