The mechanism by which I2(B) is excited in the chemical oxygen-iodine laser was studied by means of emission
spectroscopy. Using the intensity of the O2(b1&Sgr;,&ngr;'=0) → O2(X3&Sgr;,&ngr;''=0) band as a reference, I2(B) relative number densities were assessed by measuring the I2(B,&ngr;')→ I2(X,&ngr;") emission intensities. Vibrationally excited singlet
oxygen molecules O2(a1&Dgr;, &ngr;'=1) were detected using IR emission spectroscopy. The measured relative density of O2(a1&Dgr;,&ngr;'=1) for the conditions of a typical oxygen-iodine laser medium amounted to ~15% of the total O2 content. Mechanisms for I2(B) formation were proposed for both the I2 dissociation zone and the region downstream of the dissociation zone. Both pumping mechanisms involved electronically excited molecular iodine I2(A', A) as an intermediate. It has been suggested that, in the dissociation zone, the I2 A', and A states are populated in collisions with vibrationally excited singlet oxygen molecules O2(a1&Dgr;,&ngr;'). In the region downstream of the dissociation zone the intermediate states are populated by iodine atom recombination process. I2(B) is subsequently formed in collisions of I2(A',A) with singlet oxygen. We also conclude that I2(B) does not participate measurably in the I2 dissociation process and that energy transfer from O2(b1&Sgr;) does not excite I2(B) to a significant degree.