Chemical Oxygen-Iodine Laser
Definition and meaning of Chemical Oxygen-Iodine Laser in chemistry.
A chemical oxygen-iodine laser (COIL) is a powerful device that generates invisible infrared light. It uses a chemical reaction to create highly energized oxygen, which then passes its energy to iodine atoms. Those excited iodine atoms release their stored energy as a concentrated laser beam.
In more detail
Most lasers plug into a wall to get their energy from an electrical outlet. A COIL system gets its massive power completely from mixing reactive chemicals together. The process starts by reacting chlorine gas with a basic liquid mixture of hydrogen peroxide.
This turbulent reaction produces a special, high-energy form of oxygen known as singlet oxygen. This singlet oxygen is much more energetic than the ordinary triplet ground state oxygen we breathe. The machine then injects standard molecular iodine gas into this flowing stream of excited oxygen.
The energized oxygen crashes into the iodine molecules and dissociates them into single atoms. It then pumps those loose iodine atoms up into a highly excited electronic state. The excited iodine atoms cannot hold this energy and quickly relax to their ground state.
As they relax, they shoot out coherent infrared light at a wavelength of 1.315 micrometers. An optical cavity uses mirrors to bounce this light back and forth to build a laser beam. Because the fuel is purely chemical, these lasers can deliver extreme continuous power from mobile platforms. This makes them highly useful for industrial metal welding and advanced military defense programs.
Key facts
| Field | Physical Chemistry |
|---|---|
| Lasing species | Atomic iodine (I) |
| Emission wavelength | 1.315 micrometers (near-infrared) |
| Initial energy source | Singlet oxygen, O2(¹Δg) |
| Chemical fuels | Chlorine gas and basic hydrogen peroxide |
| Primary advantage | Extremely high continuous power output |
The most famous example of this technology was the Airborne Laser program operated by the military. Engineers mounted a massive megawatt-class COIL system directly inside a modified Boeing 747 airplane. The goal was to fire the chemical laser through the sky to intercept enemy missiles. It successfully proved that chemical reactions could shoot down targets from miles away.
Frequently asked questions
Why does the laser use singlet oxygen instead of ordinary oxygen?
Ordinary oxygen does not hold enough energy to excite the iodine atoms. Singlet oxygen stores about 94.3 kJ/mol of extra electronic energy. This stored energy is exactly the amount needed to power the laser.
Is a COIL considered a gas laser or a chemical laser?
It is classified as a chemical laser. Even though the actual lasing happens in a gas mixture, the raw energy to drive it comes from a chemical reaction.
Can you see the beam from a chemical oxygen-iodine laser?
No. The light emitted by the excited iodine atoms has a wavelength of 1.315 micrometers. This falls in the infrared spectrum, making it completely invisible to the human eye.