The photochemical and photophysical properties of I2in Ar, Kr, and Xe matrices have been investigated and are reported here. Following laser excitation high into the Bthinsp;3pgr;(0+u) and1pgr;ludissociative states, prompt emission is observed from theBthinsp;3pgr;(0+u),Athinsp;3pgr;1u, andAprime;thinsp;3pgr;2uelectronic states depending on the matrix host. In all matrices the emission attributed to theBelectronic state lies 200 nm to the red of the excitation wavelength and is generally featureless. The time resolved emission for this state has a detector limited rise and fall. The emission attributed to theAthinsp;3pgr;luelectronic state was resolved with a monochromator and the source determined to be thevprime;=0 level of theAstate. The lifetime for this emission is 260 mgr;s and was found to be roughly the same in all matrices. Emission from theAprime;thinsp;3pgr;2ustate was also detected but only in Xe matrices. The measured lifetime for this state was 6.3 ms. Data from a number of previous experiments on matrix isolated halogens in Ar, Kr, and Xe are reviewed and a consistent model for the relaxation pathways for intramolecular electronic energy transfer is presented. The implications of this model for studies of the solvent cage effect on I2photodissociation and the development of the I2chemical laser are also discussed.
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