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An experiment is presented in which the fluorescent lifetime versus pressure of excited I2 is studied. Variation in fluorescent lifetime when different quenching gases are added is also examined. A doubled Nd:YAG laser is used to excite fluorescence in iodine vapor. This pulsed 532 nm source is ideal for such measurements and the experiment is a nice complement to spectroscopic studies commonly done on iodine in undergraduate or graduate laboratory courses in physical chemistry or spectroscopy. Students acquire hands-on experience with lasers, vacuum manipulations, oscilloscopes, and computerized instrumentation. The emission intensity follows first-order decay kinetics and linear Stern–Volmer plots are obtained of rate constant versus pressure of quenching gas. Using gas kinetic theory, cross sections are deduced for quenching by He, Ne, Ar, Kr, H2, N2, O2, CO2, SF6, and I2 and values for 532 nm excitation are reported for the first time. Two theoretical models for the cross sections are examined and one is found to fit the measurements better than the other.