Dynamical constraints on the transfer of angular momentum in rotationally inelastic collisions of I2(B 3Π) with He and Xe

We have measured thermally averaged level‐to‐level rate constants for rotationally inelastic collisions of I2(B 3Π) with Xe and He using the method of laser induced fluorescence. We present the values of 149 rate constants with average errors less than 10% for initial rotational levels ranging from 41 to 113 in the v′ = 13 vibrational level. For I*2–He, we report the first experimental evidence for a limitation of maximum angular momentum transfer on level‐to‐level rate constants and conclude that dynamical, rather than energetic constraints govern the collisional process. We find that the I*2–Xe rate constants follow a power law in both energy and angular momentum transfer, a behavior observed in most previous experimental work on rotationally inelastic collisions.