FEMTOSECOND ACTIVATION OF REACTIONS AND THE CONCEPT OF NONERGODIC MOLECULES

The description of chemical reaction dynamics often assumes that vibra tional modes are well coupled (ergodic) and redistribute energy rapidl y with respect to the course of the reaction. To experimentally probe nonergodic, nonstatistical behavior, studies of a series of reactions induced by femtosecond activation for molecules of varying size but ha ving the same reaction coordinates [CH,(2) - (CH2,),(n-2), - C = O dag ger --> products, with n = 4, 5, 6, and 10] were performed. Comparison of the experimental results with theoretical electronic structure and rate calculations showed a two to four orders of magnitude difference , indicating that the basic assumption of statistical energy redistrib ution is invalid. These results suggest that chemical selectivity can be achieved with femtosecond activation even at very high energies.