Historical perspective of COIL

Abstract

The oxygen-iodine laser was the first electronic transition chemical laser. It first lased 25 years ago at the Air Force Weapons Laboratory (now the Air Force Research Laboratory). The development started several years earlier and involved the support of many people in the laser community. I would like to describe the early thoughts, insights and even misconceptions that we had in the early days. I will also highlight the contributions of many of the people and organizations that contributed to the early development of the COIL laser. A Brief Background on 02( 1 Ag)Chemical sources of O2(Ag) have been known for many years. Mallet [1] first reported the red glow obtained when hypochlorite solution and hydrogen peroxide was mixed. The O2(Ag) molecule was first identified by Herzberg in the spectrum of the sun in 1934. Groh [2] mentions the red chemiluminescence obtained when gaseous chlorine or bromine is added to basic hydrogen peroxide. Later, Groh & Kirriman [3] mixed gaseous chlorine with KOH and hydrogen peroxide and proposed that the red glow is from two O2('Ag) molecules colliding. Later, Seliger [4] published the spectra of the hypochlorite -peroxide reaction in the red at 634 nm. For me, the seminal article on excited oxygen was Khan and Kasha [5]. Even though the chemical process that produced a metastable electronically excited species was known, the marriage of oxygen and iodine came in discharge studies. Iodine and O2(CAg)The reaction of iodine and discharged oxygen was first reported by Ogryzlo and his group [6]. They observed that when iodine was added to excited oxygen, a bright yellow glow was seen. This was recognized as 12 B state emission. They also observed a strong emission at 1.315 ýi, the iodine atom 2 P 1 / 2 2 P3/ 2 transition. The excitation of the iodine was attributed to the near resonant pumping by 02( 1 Ag) . The iodine atoms were thought to be formed by the dissociation of molecular iodine by O2(Tu). This work didn't attract the-attention of the laser community until later. In 1969, Elmer Ogryzlo went on sabbatical to Brian Thrush's laboratory in England. There he suggested the oxygen-iodine system as an interesting system for Thrush's graduate student, R. G. Derwent. The suggestion generated several papers [7], [8], [9], [10], and [11]. In their third paper, they suggested that an inversion could be achieved on the iodine atom 2 pv 2 -2 P 3 / 2 transition if a sufficient O2(Ag) fraction could be produced. Using the equilibrium constant for the energy pumping reaction, They showed a flow containing about 15% O2(OAg) could produce an inversion on the iodine 2 P 112 -2 P 3 / 2 transition. It was radical to propose an equilibrium as a pumping reaction -in a two level system terminating in the ground state! was looking for research projects of interest to the Air Force. I had visited the AFWL the previous year and met a number of the technical people there. In the summer of 1973, I began working on electronic transition chemical lasers. The initial funding for the effort was $1...

Historical perspective of COIL diagnostics

“…They detected 1 2 (X; 25•v"•43) using laser induced fluorescence to probe the products of this quenching process. Following up on this excellent work, we used laser induced fluorescence to probe the dissociation region in a flow of singlet oxygen and molecular iodine and observed a similar distribution of vibrationally hot ground state 12.21 This combined with the prior chemiluminescence results of Heidner, 13 1 4 Lilenfeld, 2223 and Alsing, 17 confirmed that iodine was an active participant in its own dissociation.…”

“…3 , 4 Using a microwave source for excited oxygen and a temperature controlled flow reactor, they produced kinetic data that are used to this day. From these data they developed possible mechanisms for the molecular iodine dissociation that were discussed earlier by Mike Heaven.…”

“…1- 3 The excellent reviews of the laser development and COIL kinetics by Bill McDermott 4 and Mike Heaven 5 earlier in this volume provide ample motivation for a discussion of diagnostics.…”

The Measurement of Gain in a Supersonic, Combustion-Driven Generator for NCl(a1Delta)

“…The history and development of COIL has been well documented by McDermott [6], Heaven [7], and others [8]. The first continuous wave AGIL device, demonstrated by Henshaw in 2000 [3], was enabled and inspired by the work of many, including Benard [9], Bower [10,11], Clyne [12][13][14], Coombe and Gilbert [15][16][17][18][19], Heaven [7,20,21], Henshaw [22,23] …”