The different lifetimes of the two molecules are due to the dynamic evolution between the time the molecules reach the S3 minimum and the time they convert to the S2 state. The S3→S2 hopping can happen at the entire puckering space of the 6-membered ring, and the planar minimum of 6-AIH + allows easy access to such conformations. In the case of 7-AIH + , with a pre-Dewar S3 minimum, access to S3→S2 hopping region depends on either increasing the puckering degree of the boat conformation or moving away to some other puckering region.