Electron-molecule scattering cross-sections. I. Experimental techniques and data for diatomic molecules

An overview is presented of experimental and theoretical research in the field of physics and engineering of singlet delta oxygen (SDO) production in low-temperature plasma of various electric discharges. Attention is paid mainly to the SDO production with SDO yield adequate for the development of an electric discharge oxygen–iodine laser (DOIL). The review comprises a historical sketch describing the main experimental results on SDO physics in low-temperature plasma obtained since the first detection of SDO in electric discharge in the 1950s and the first attempt to launch a DOIL in the 1970s up to the mid-1980s when several research groups started their activity aimed at DOIL development, stimulated by success in the development of a chemical oxygen–iodine laser (COIL). A detailed analysis of theoretical and experimental research on SDO production in electric discharge from the mid-1980s to the present, when the first DOIL has been launched, is given. Different kinetic models of oxygen low-temperature plasma are compared with the model developed by the authors. The latter comprises electron kinetics based on the accompanying solution of the electron Boltzmann equation, plasma chemistry including reactions of excited molecules and numerous ion–molecular reactions, thermal energy balance and electric circuit equation. The experimental part of the overview is focused on the experimental methods of SDO detection including experiments on the measurements of the Einstein coefficient for SDO transition and experimental procedures of SDO production in self-sustained and non-self-sustained discharges and analysis of different plasma-chemical processes occurring in oxygen low-temperature plasma which brings limitation to the maximum SDO yield and to the lifetime of the SDO in an electric discharge and its afterglow. Quite recently obtained results on gain and output characteristics of DOIL and some projects aimed at the development of high-power DOIL are discussed.

https://iopscience.iop.org/article/10.1088/0022-3727/40/2/R01/pdf

Physics and engineering of singlet delta oxygen production in low-temperature plasma

Chemical oxygen-iodine lasers (COIL) are attractive for diverse industrial applications because they are capable of high efficiency, high power operation, and because the 1.315μm wavelength can be transmitted through fiber optics and couples efficiently with most metals. Conventional COILs are pumped with O2(Δ1) that is generated by reaction of Cl2 in a basic H2O2 solution. Current trends in pumping COILs involve producing the O2(Δ1) in electric discharges, thereby circumventing the hazards, complexity, and weight associated with pumping and storing caustic liquids. In this work, we have investigated the scaling of O2(Δ1) yields with specific energy deposition in He∕O2 mixtures in flowing radio frequency (rf) discharges at pressures of a few to tens of Torr using a global plasma kinetics model. We found that O2(Δ1) yield increases nearly linearly with specific energy deposition in O2 molecules up to a few eV per molecule, with yields peaking around 30% by 5–8eV. Further increases in specific energy deposi...

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O2(Δ1) production in He∕O2 mixtures in flowing low pressure plasmas

Efficient extraction of chemically generated O2(1Δ) energy has been obtained in a trasverse‐flow oxygen‐iodine laser. The measured power extraction efficiency with off‐optimal outcoupling was 15%. Output powers in excess of 100 W were obtained for periods of up to 3 min.

Efficient operation of a 100‐W transverse‐flow oxygen‐iodine chemical laser

Laser action at 1315nm on the I(P1∕22)→I(P3∕22) transition of atomic iodine is conventionally obtained by a near-resonant energy transfer from O2(a1Δ) which is produced using wet-solution chemistry. The difficulties in chemically producing O2(a1Δ) has motivated investigations into purely gas phase methods to produce O2(a1Δ) using low-pressure electric discharges. In this letter, we report on the demonstration of a continuous-wave laser on the 1315nm transition of atomic iodine where the O2(a1Δ) used to pump the iodine was produced by a radio-frequency-excited electric discharge. The electric discharge was sustained in a He∕O2 gas mixture upstream of a supersonic cavity which is employed to lower the temperature of the continuous gas flow and shift the equilibrium of atomic iodine in favor of the I(P1∕22) state. The laser output power was 220mW in a stable cavity composed of two 99.99% reflective mirrors.

Continuous-wave laser oscillation on the 1315nm transition of atomic iodine pumped by O2(a1Δ) produced in an electric discharge

cw laser action was achieved on the 2P1/2→2P3/2 transition of the iodine atom by energy transfer from the 1Δ metastable state of O2. The excited oxygen was generated chemically by flowing chlorine gas through a basic solution of 90% H2O2. The effluent from the oxygen generator was mixed with molecular iodine at the entrance of a longitudinal flow laser cavity where the I2 was dissociated by a small amount of O2(1Σ) that was present in the flow due to energy pooling processes. The measured output power was greater than 4 mW.

An electronic transition chemical laser

An observation concerning the radiative lifetime of the O*4 van der waals complex

This report covers unclassified laser research performed at the Air Force Weapons Laboratory. The two reports included herein describe the first operation of an oxygen-iodine chemical laser and the first transverse flow high efficiency oxygen-iodine chemical laser.

N. R. Pchelkin

Papers

An electronic transition chemical laser

Efficient operation of a 100‐W transverse‐flow oxygen‐iodine chemical laser

An observation concerning the radiative lifetime of the O*4 van der waals complex

An electronic transition chemical laser. Final report