Toward understanding the dissociation of I2 in chemical oxygen-iodine lasers:: Combined experimental and theoretical studies

The dissociation of I-2 molecules at the optical axis of a supersonic chemical oxygen-iodine laser (COIL) was studied via detailed measurements and three-dimensional computational fluid dynamics calculations. The measurements, briefly reported in a recent paper [Rybalkin , Appl. Phys. Lett. 89, 021115 (2006)] and reanalyzed in detail here, revealed that the number N of consumed O-2(a (1)Delta(g)) molecules per dissociated I-2 molecule depends on the experimental conditions: it is 4.5 +/- 0.4 for typical conditions and I-2 densities applied for optimal operation of the COIL but increases at lower I-2 densities. Comparing the measurements and the calculations enabled critical examination of previously proposed dissociation mechanisms and suggestion of a mechanism consistent with the experimental and theoretical results obtained in a supersonic COIL for the gain, temperature, I-2 dissociation fraction, and N at the optical axis. The suggested mechanism combines the recent scheme of Azyazov and Heaven [AIAA J. 44, 1593 (2006)], where I-2(A(') (3)Pi(2u)), I-2(A (3)Pi(1u)), and O-2(a (1)Delta(g),v) are significant dissociation intermediates, with the "standard" chain branching mechanism of Heidner III [J. Phys. Chem. 87, 2348 (1983)], involving I(P-2(1/2)) and I-2(X (1)Sigma(+)(g),v). (c) 2007 American Institute of Physics.