The I2 dissociation mechanisms in the chemical oxygen-iodine laser revisited

Abstract

The recently suggested mechanism of I(2) dissociation in the chemical oxygen-iodine laser (COIL) [K. Waichman, B. D. Barmashenko, and S. Rosenwaks, J. Appl. Phys. 106, 063108 (2009); and J. Chem. Phys. 133, 084301 (2010)] was largely based on the suggestion of V. N. Azyazov, S. Yu. Pichugin, and M. C. Heaven [J. Chem. Phys. 130, 104306 (2009)] that the vibrational population of O(2)(a) produced in the chemical generator is high enough to play an essential role in the dissociation. The results of model calculations based on this mechanism agreed very well with measurements of the small signal gain g, I(2) dissociation fraction F, and temperature T in the COIL. This mechanism is here revisited, following the recent experiments of M. V. Zagidullin [Quantum Electron. 40, 794 (2010)] where the observed low population of O(2)(b, v = 1) led to the conclusion that the vibrational population of O(2)(a) at the outlet of the generator is close to thermal equilibrium value. This value corresponds to a very small probability, ∼0.05, of O(2)(a) energy pooling to the states O(2)(X,a,b, v > 0). We show that the dissociation mechanism can reproduce the experimentally observed values of g, F, and T in the COIL only if most of the energy released in the processes of O(2)(a) energy pooling and O(2)(b) quenching by H(2)O ends up as vibrational energy of the products, O(2)(X,a,b), where the vibrational states v = 2 and 3 are significantly populated. We discuss possible reasons for the differences in the suggested vibrational population and explain how these differences can be reconciled.

Dissociation of Molecular Iodine in a Flow Tube in the Presence of O2(1Σ) Molecules

“…This is much less than the value of 7.5 × 10 –15 cm 3 s –1 proposed for the first reaction to explain dthe issociation rate via this cascade mechanism . For the cascade mechanism where I 2 * = I 2 ( 3 Π 2u ), it was suggested that I 2 ( 3 Π 2u ) can be produced much more efficiently in collisions of I 2 with O 2 (a, v ≥ 1), which can be formed in reaction . ,− Excited molecules I 2 ( 3 Π 2u ), O 2 (a, v ≥ 1), and I 2 (X, v > 20) play an important role in COIL modeling as intermediates in the initiation and chain stages of iodine dissociation. ,, …”

“…10,12−15 Excited molecules I 2 ( 3 Π 2u ), O 2 (a,v ≥ 1), and I 2 (X,v > 20) play an important role in COIL modeling as intermediates in the initiation and chain stages of iodine dissociation. 12,14,15 Experiments performed in refs 9, 10, and 13 were done at high initial concentrations of molecular iodine. Under these conditions, the contribution of the initiating stage into the total dissociation rate was very small compared to the chain stage.…”