Kinetics of light emission from excited states of molecular iodine produced in the pulse radiolysis of gaseous argon--iodine mixtures

Light emission from molecular iodine has been studied in the time regime of ca. 20-1000 ns following the radiolysis of argon-iodine systems with 10-8-s pulses. Several emission maxima were observed in the 280-530-nm region, corresponding to emission from known excited states of molecular iodine. The temporal characteristics of the emission are independent of wavelength; the intensity of the emission at 342 nm is the greatest by a factor of about 300. Detailed kinetic studies of the emission at 342 nm show that the emitting state is produced as a result of a sequence of ionic reactions, as well as by a nonionic sequence. The fact that the emission spectrum is the same for both sequences indicates a common precursor of the emitting state. Furthermore, the independence of the kinetics on wavelength indicates that the precursor must be common to all of the emitting states of I2. A mechanism is suggested which involves the production of excited iodine atoms and subsequent energy transfer to I2. These results are relevant to the current interest in the 342-nm emission band as a laser