Parameters relevant to the operation of an electron-beam initiated atomic iodine laser, which would lase on the transition 5 2P1/2 (I*)→5 2P3/2 (I), have been measured by pulse radiolysis. Kinetic data for the parent compound quenching of I* were obtained by variation of the parent compound pressure at constant buffer gas pressure and observing I* decay rates versus time. Deactivation rates for perfluoroalkyl iodides were found to be much lower than for the corresponding alkyl iodides. Values obtained (in cm3 molec−1 s−1) are as follows: CH3I, (2.0±0.1)×10−13; C2H5I, (5.0±0.3)×10−13; CF3I, (8.8±0.3)×10−16; C2F5I, (9.7±1.0)×10−15; n-C3F7I, (2.5±0.2)×10−15; i-C3F7I, (1.7±0.1)×10−15; n-C4F9I, (1.8±0.1)×10−14. The extent of population inversion was investigated by measuring initial excited state and ground state atomic iodine concentrations, which gives the branching ratio [I*]/[I]. Values obtained are as follows: CH3I, 2.7; CF3I, 3.8; C2F5I, 2.7; i-C3F7I, 3.2; n-C4F9I, 1.8. Comparing both branching ratios and lifetimes, it is seen that CF3I is the most promising candidate for an electron beam initiated atomic iodine laser.