Experimental and theoretical study of distribution of O2 molecules over vibrational levels in O2(a 1Δg)–I mixture

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The vibrationally excited oxygen in O2(a 1Δg)–I mixture was detected by emission spectroscopy. The analysis of a luminescence spectra of oxygen molecules on O2(b 1Σg+,v′)→O2(X 3Σg−,v″) transitions has shown that vibrationally excited O2(b 1Σg+) molecules up to v=5 are generated in the active medium of chemical oxygen–iodine laser (COIL). The highest values of relative O2(b 1Σg+,v=1) population of 22±2% and O2(b 1Σg+,v=2) of 10±3.5% are reached for I2 content in an oxygen flow ≈1%. It is shown theoretically that the relative populations of O2(X 3Σg−), O2(a 1Δg), and O2(b 1Σg+) molecules at the first and the second vibrational levels are approximately equal because of fast EE energy exchange between oxygen molecules. Up to 20% of oxygen molecules in COIL active medium are vibrationally excited. Comparison of intensities of O2(b 1Σg+,v′)→O2(X 3Σg−,v″) bands has demonstrated that a few percent of O2(b 1Σg+,v) molecules are vibrationally excited with v=3, 4, or 5. It is suggested that the following pooling reaction forms them: O2(a 1Δg,v=i)+I(2P1/2)→O2(b 1Σg+,v′=i+2)+I(2P3/2), where i=1, 2, or 3.