Barrier height titration by tunable photoionization combined with chemical monitoring: Unimolecular keto/enol tautomerization of the acetamide cation radical

Abstract : By using a new "titration" technique, the activation barrier for the strictly unimolecular 1,3-hydrogen migration 1*+ ? 2*+ has been determined (0.74 ± 0.06 eV; see reaction profile). With this technique the internal energy of 1*+ is controlled by variable photoionization of acetamide and the chemistry of the resulting enol ion 2*+ is then probed by structure- specific ion - molecule reactions.