Mechanism and kinetics of iodine dissociation in COIL

Abstract

Dissociation of 12 by 0 2 (a'A), with subsequent excitation of I*, was first observed by Arnold et al.' in 1966. This key discovery led to the eventual development of the chemical oxygen iodine laser (COIL). The mechanism by which 12 is dissociated was not determined by Arnold et al. ' and has remained elusive, despite many experimental attempts to unravel this question. Although the details are not known, it is apparent that a complex interplay between vibrationally and electronically excited states of 1L is involved. Vibrationally excited states of 02 have also been implicated. Characterization of the dissociation process is an important issue for COIL as the efficiency is impacted by the energy cost of dissociating the iodine. In this paper we provide a historical summary of work on the dissociation mechanism, and summarize the current understanding of the problem.

Historical perspective of COIL diagnostics

“…This was discussed in detail in Mike Heaven's paper earlier in this volume. 5 From the above, we can deduce that knowledge of the concentrations of 0,('A), O 2 ( 3 Z), 1(2P 112 ). I(2P 3 2), and temperature are crucial.…”

“…From these data they developed possible mechanisms for the molecular iodine dissociation that were discussed earlier by Mike Heaven. 5 These data have withstood the test of time for nearly two decades and comparisons continue to be made between new models for the dissociation to the data-base produced by this excellent work.…”

“…These systems use Beer's law to determine the concentration, N, of the target species as described in Eq. (5).…”

“…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.…”