Energy transfer in a photochemical iodine laser

doi:10.1016/0009-2614(72)80235-5

Chemical Physics Letters

Volume 14, Issue 4, 15 June 1972, Pages 445-448

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Abstract

Small-signal gain measurements have been used to determine the decay of excited atoms l(5²P $12$ after flash photolysis of CF₃l. A rate coefficient for the deactivation of iodine by CF₃l is obtained. The measurements confirm that in addition to the photolysis another yet unexplained pumping process contributes to the population inversion. The method used here is generally applicable to kinetic studies in systems where suitable laser sources are available.

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The temperature regime, in which iodine photodissociation lases operate, depends on the UV pumping intensity and on the heat capacity of laser mixture. Even though low temperatures are preferred, pyrolysis conditions are reported, too. To distinguish between the nonpyrolytic and pyrolytic regimes, a simple experimental method of finding the pyrolysis limit was suggested. The chain of processes, which may supplement the pyrolytic decomposition of C₃F₇I as a laser gas, is reported. Special attention was paid to the production and reactions of different kinds of radicals. Moreover, possible reactions of exposed gas mixture with laser tube construction materials and with gaseous impurities are also discussed.
Gas phase radiolysis of CF<inf>3</inf>I-CH<inf>3</inf>I mixtures
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The gas phase radiolysis of equimolar mixtures of methyl iodide and trifluoromethyl iodide was studied at 200 torr (26.7 kPa) pressure both pure and with 10% added oxygen. For the pure system 21 products were identified and their yields measured. The major products and their G-values are: HI, 1.56; HF, 1.04; I₂, 0.76; H₂, 0.42; CH₄, 0.35; C₂H₆, 0.25; CF₃H, 0.34; CH₂I₂, 3.08; and C₂F₄I₂, 0.26. Minor products include CF₄, C₂F₆, C₂F₄, C₂H₄, C₂H₂, C₂H₂F₂, CH₃CF₃, C₂F₃H, C₂F₂HI, C₂F₃I, C₂F₅I and C₂H₂F₃I. The addition of 10% oxygen reduced the products significantly except that the C₂H₄, CHF₃ and I₂ yields were enhanced. Although ionic pathways contribute to formation of some products, rupture of the weak C-I bond in both reactants is of major importance in this system. Attack of the resulting CF₃⋅ and CH₃⋅ radicals on substrate (especially CH₃I) via abstraction and displacement reactions accounts for most of the major product yields. The overall yield for decomposition of CH₃I during radiolysis of the mixtures exceeds the yield for decomposition of CF₃I by a factor of nearly three.
Spin-orbit relaxation of HTe (X<sup>2</sup>Π<inf> 1 2</inf>)
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Electronically excited HTe(X²Π_$12$) radicals have been observed following the isothermal flash photolysis of H₂Te. Spin-orbit relaxation to the electronic ground state, HTe(X²Π_$32$), has been monitored and the cross-section for relaxation by argon determined as σ = (4.6 ± 3.5) × 10⁻²⁰ cm². This value is significantly larger than that for the isoelectronic atom I(5²P_$12$). The production of HTe(X²Π_$12$) in the primary photochemical step is discussed within the context of a correlation diagram using double groups (groups in which spin is included in the total representation).
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^☆: Work supported by the Bundesministerium für Bildung und Wissenschaft within the technology program.

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Energy transfer in a photochemical iodine laser☆

Abstract

Appl. Phys. Letters

Soviet Phys. JETP

JETP Letters

J. Appl. Phys.

J. Appl. Phys.