Chemical Oxygen-Iodine Laser
Definition and meaning of Chemical Oxygen-Iodine Laser in chemistry.
A chemical oxygen-iodine laser (COIL) is a device that generates coherent infrared light by using energy released from a chemical reaction to excite singlet oxygen, which then transfers that energy to atomic iodine to produce laser emission.
In more detail
Chlorine gas is reacted with a basic solution of hydrogen peroxide to generate excited singlet-state molecular oxygen, O2(¹Δg), which is far more energetic than the ordinary triplet ground state. This singlet oxygen collides with molecular iodine, dissociating it into iodine atoms and pumping them into an excited electronic state. The excited iodine atoms then relax to their ground state, emitting coherent light at 1.315 micrometers, which is amplified into a laser beam within an optical cavity. Because the energy comes from a chemical reaction rather than electricity, COIL systems can deliver very high continuous power in a compact package, making them useful for industrial cutting and welding, high-power military and defense research, and specialized materials-processing applications.
Key facts
| Field | Physical Chemistry |
|---|---|
| Lasing species | Atomic iodine, I |
| Emission wavelength | 1.315 micrometers (near-infrared) |
| Energy source | Singlet oxygen, O2(¹Δg) |
In the Airborne Laser (YAL-1) program, a COIL system generated a megawatt-class beam intended to intercept ballistic missiles during their boost phase.
Frequently asked questions
Why is singlet oxygen used instead of ordinary oxygen?
Singlet oxygen, O2(¹Δg), stores about 94.3 kJ/mol of electronic excitation energy above the ordinary triplet ground state, O2(³Σg⁻). This stored energy is exactly enough to excite iodine atoms to the state needed for lasing, whereas ground-state oxygen cannot do this.
Is COIL a gas laser or a chemical laser?
COIL is classified as a chemical laser because the population inversion is created directly by a chemical reaction (chlorine plus basic hydrogen peroxide) rather than by an electrical discharge or lamp, even though the lasing medium is a flowing gas mixture.