Iodine Kinetic Energy: A Monitor for Dynamics of and Structure of Radicals Produced in the Photodissociation of Organic Iodides
The technique of state-selective one dimensional photofragmentation translation energy spectroscopy is developed and the velocity of the one photon photodissociated iodine in the 2P3/2 and 2P1/2 states is determined for C2F5I as well as for axial and equatorial iodocyclohexane.
The velocity, and thus the kinetic energy, of the iodine atoms produced in the ground state from the photodissocition of C2F5I is found to be sensitive to the laser polarization direction with respect to the detection axis. This can be explained by proposing that ground state iodine atoms are produced as a result of absorption to two repulsive states with oppositive polarization characteristics. One state gyves the iodine atoms directly, while the other crosses to another state that produces the iodine. It is further concluded that energy redistribution occurs during the curve crossing process, leading to less kinetic energy for the dissociated iodine atoms formed from the latter mechanism.
The 304.0 nm photodissociation of the axial iodocyclohexane is found to produce excited iodine atoms with more kinetic energy than those produced from the photodissociation of equatorial iodocyclohexane. This is in spite of the fact that the excited nonbonding electrons on the iodine in the axial position is more strongly coupled to the ring hydrogens than in the equatorial position. This result suggests that the cyclohexyl radical produced from the photodissociation of the axial iodocyclohexane (i.e., the equatorial radical) has less internal energy than that produced from the photodissociation of equatorial iodocyclohexane (i.e., the axial radical). This suggests that the ground state of the cyclohexyl radical has an equatorial configuration.
KeywordsAnisotropy Iodine Iodide Photodissociation Cyclohexyl
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