Investigation of the Excited State Iodine Lifetime in the Photodissociation ot r ' ernuoroaikyi iodides by Stephen

The development of a space-based solar pumped laser system has been the focus of NASA research for several years. This laser would have application in power transmission to space vehicles and bases on the moon or Mars, where it could provide a means of electric power generation, propulsion, and communication[l]. An evaluation of prospective laser materials over the past decade has resulted in the identification of the iodine photodissociation laser as that system best suited to solar-pumped high energy operation[2]. The active medium for the solar-pumped iodine photodissociation laser is from the family of perfluoroalkyl iodides. These lasants have the general form CnF2n÷lI, o_en abbreviated as RI. These iodides are known to exhibit photodissociation of their CI bond when irradiated by near UV photons. Though many isomers have been tested with regard to their solar pumping properties, the iodide t-C4F9I has been identified as the most promising material for high-power application. C4FgI is an attractive candidate for a lasant in that: 1) its absorption curve is shifted toward longer wavelengths in comparison to other iodides, allowing a greater absorption of the available solar radiation, and 2) the formation of R2 dimers appears to be greatly limited. This subsequently results in greater recombination to the original RI molecule and a decreased production of the iodine molecule I2, which is known to inhibit lasing action. The excited state lifetime of the active medium is a very important parameter in a laser system. It governs the ability of a laser amplifier to store energy. The excited iodine atom has a long natural radiative lifetime ( 130 msec), giving the potential for high gain in the laser system[3]. However, non-radiative processes such as quenching by the parent RI molecule can shorten the lifetime considerably. If the lifetime is reduced too severely, the material ceases to be an effective lasant. Therefore, when attempting to develop theoretical models to