ABSTRACT
The chemical oxygen iodine laser (COIL) [1] is the only known example of a high-power chemically driven electronic transition laser. Unlike other chemical lasers (e.g. HF (hydrogen fluoride) and DF (deuterium fluoride) lasers), which operate on rotational–vibrational transitions of molecules, the COIL operates on an atomic electronic transition. At present the COIL is the shortest wavelength chemical laser system [2,3]. Figure 33.1 shows the electronic states of the species participating in the pumping process of the COIL. The laser transition, at 1315 nm, takes place between the spin-orbit levels of the ground-state configuration of the iodine atom, I(5p52P1/2) → I(5p52P3/2). Basic chemical reactions taking place in the COIL are presented in Table 33.1 [4,5]. The iodine atoms are pumped by a near-resonant energy transfer from oxygen molecules in the excited singlet delta state, O2(a1 ∆g) (reaction 1, Table 33.1). O2(1∆) is a metastable molecule with a very long radiative lifetime (76 min) [6] and a pronounced stability against collisional deactivation processes in many environments. Hence, it can be used as the energy carrier for the COIL. Mixing of chemically produced O2(1∆) with I2 molecules results in dissociation of molecular iodine to atomic iodine which is subsequently excited via reaction 1 (Table 33.1).
