Direct Experimental Evidence for Dissociative Photoionization of Oxygen Molecule via (2)Σ(u)(-) Ionic "Optical Dark" State.
Summary of "Direct Experimental Evidence for Dissociative Photoionization of Oxygen Molecule via (2)Σ(u)(-) Ionic "Optical Dark" State."
Direct experimental evidence for dissociative photoionization of oxygen molecule via the (2)Σ(u)(-) ionic optical dark state is presented by an investigation using the method of threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging. Besides vibrational progress of the B(2)Σ(g)(-) state, several weak vibrational bands of the (2)Σ(u)(-) ionic optical dark state are observed concomitantly in an excitation energy range of 20.2-21.1 eV. Only O(+) fragments are detected in the whole excitation energy range; therefore, all vibrational bands are completely predissociative. TPEPICO three-dimensional time-sliced velocity images of O(+) fragments dissociated from vibrational state-selected O(2)(+)((2)Σ(u)(-),v(+)) ions are recorded. For the (2)Σ(u)(-)(v(+)=0-3) vibrational states, only the lowest dissociation channel of O(+)((4)S) + O((3)P) is observed. Once the photon energy is slightly increased to the (2)Σ(u)(-)(v(+)=4) level, a new concentric doughnut appears in the image, indicating that the second dissociation channel of O(+)((4)S) + O((1)D) is identified indeed. With the aid of potential energy curves, the dissociative mechanism of O(2)(+) in the (2)Σ(u)(-)(v(+)) state is proposed.
Affiliation
Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China , Hefei, Anhui 230026, China.
Journal Details
This article was published in the following journal.
Name: The journal of physical chemistry. A
ISSN: 1520-5215
Pages: 9459-65
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/22946501
- DOI: http://dx.doi.org/10.1021/jp3034038
Medical and Biotech [MESH] Definitions
Oxygen Compounds
Inorganic compounds that contain oxygen as an integral part of the molecule.
Anaerobic Threshold
The oxygen consumption level above which aerobic energy production is supplemented by anaerobic mechanisms during exercise, resulting in a sustained increase in lactate concentration and metabolic acidosis. The anaerobic threshold is affected by factors that modify oxygen delivery to the tissues; it is low in patients with heart disease. Methods of measurement include direct measure of lactate concentration, direct measurement of bicarbonate concentration, and gas exchange measurements.
Mixed Function Oxygenases
Widely distributed enzymes that carry out oxidation-reduction reactions in which one atom of the oxygen molecule is incorporated into the organic substrate; the other oxygen atom is reduced and combined with hydrogen ions to form water. They are also known as monooxygenases or hydroxylases. These reactions require two substrates as reductants for each of the two oxygen atoms. There are different classes of monooxygenases depending on the type of hydrogen-providing cosubstrate (COENZYMES) required in the mixed-function oxidation.
Nervous System Autoimmune Disease, Experimental
Experimental animal models for human AUTOIMMUNE DISEASES OF THE NERVOUS SYSTEM. They include GUILLAIN-BARRE SYNDROME (see NEURITIS, AUTOIMMUNE, EXPERIMENTAL); MYASTHENIA GRAVIS (see MYASTHENIA GRAVIS, AUTOIMMUNE, EXPERIMENTAL); and MULTIPLE SCLEROSIS (see ENCEPHALOMYELITIS, AUTOIMMUNE, EXPERIMENTAL).
Prejudice
A preconceived judgment made without adequate evidence and not easily alterable by presentation of contrary evidence.
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