Discharged generator of singlet oxygen for oxygen-iodine laser. Transport kinetics of O2(a 1δg) and O2(b 1σ g + ) molecules and O(3 P) atoms in Ar:O2 and He:O2 flows excited by a 13.56-MHz discharge
| Autor: | K. S. Klopovsky, O.V. Braginsky, A. T. Rakhimov, A. N. Vasil’eva, Tatyana Rakhimova, D. V. Lopaev, A.S. Kovalev |
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| Rok vydání: | 2006 |
| Předmět: |
Materials science
Argon Quenching (fluorescence) Singlet oxygen Analytical chemistry chemistry.chemical_element Condensed Matter Physics Oxygen Industrial and Manufacturing Engineering Atomic and Molecular Physics and Optics law.invention chemistry.chemical_compound chemistry law Excited state Atomic physics Gas-filled tube Total pressure Inert gas Instrumentation |
| Zdroj: | Laser Physics. 16:1161-1174 |
| ISSN: | 1555-6611 1054-660X |
| DOI: | 10.1134/s1054660x06080020 |
| Popis: | To understand and reveal the basic physical factors providing the possibility of scaling of a discharged singlet oxygen generator (DSOG) in an oxygen-iodine laser, the production, and transport kinetics of metastable O2(a 1δg) and O2(b 1σ g + ) molecules, as well as O(3 P) atoms, were investigated in Ar:O2 and He:O2 gas flows excited by a 13.56-MHz discharge in a wide range of pressures (4–40 Torr) and oxygen percentages. It is shown that the densities and transport kinetics of O2(a 1δg), O2(b 1σ g + ), and O(3 P) appear similar for oxygen mixtures with argon and helium in the same conditions independent of discharge mode. Compared to pure O2, the dilution of oxygen with an inert gas allows higher energy inputs per an oxygen molecule to achieved, especially under conditions of the homogeneous discharge mode (α-mode), which gives a higher efficiency of O2(a 1δg) excitation in Ar:O2 and He:O2 mixtures. But the maximum attainable yield of singlet oxygen in Ar:O2 and He:O2 at fixed partial O2 pressure is found to be comparable with the O2(a 1δg) yield in pure oxygen at the same pressure. The reason for this is the increased three-body deactivation of O2(a 1δg) by atomic oxygen in the mixtures because of the greater total pressure. The estimation of the rate constant of O2(a 1δg) three-body quenching by O(3 P) in Ar:O2 and He:O2 mixtures as (1.5 ± 0.5) × 10−32 cm6/s was carried out from the analysis of transport kinetics of singlet and atomic oxygen in the discharge afterglow at high pressures exceeding ∼10 Torr. A similar analysis for the lower pressures has revealed that losses both of metastable O2(a 1δg) and O2(b 1σ g + ) molecules, and of O(3 P) atoms on the surface of the discharge tube, are determined by the density of each of the components. The obtained loss probabilities of O2(a 1δg), O2(b 1σ g + ), and O(3 P) on the silica surface show that the surface loss probabilities of all the species can increase noticeably under the discharge exposure. Thus, the key parameters determining the maximal O2(a 1δg) yield in the DSOG are a homogeneous volumetric mode of the discharge, energy input per oxygen molecule in this mode, and a low rate of O2(a 1δg) quenching. Just three-body quenching of O2(a 1δg) by O(3 P) limits the singlet oxygen yield with increasing pressure. The fast removal of atomic oxygen both in discharge and in the earlier afterglow could provide DSOG scaling with pressure. |
| Databáze: | OpenAIRE |
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