Photodestruction of Adenosine [Formula presented]-Monophosphate (AMP) Nucleotide Ions in vacuo: Statistical versus Nonstatistical Processes

The lifetimes of both deprotonated adenosine [Formula presented]-monophosphate (AMP) and protonated AMP, after 266-nm photon absorption and intramolecular vibrational redistribution, were determined to be [Formula presented] based on a newly developed heavy-ion storage ring technique. Protonation of the adenine nucleobase seriously affects the fragmentation mechanism: the major part of the photoexcited anions fragment in a statistical (ergodic) process, whereas nearly all the cations ([Formula Presented]) fragment in a nonergodic process. In solution at natural [Formula presented] the AMP anion is prevalent and photoproduct formation is therefore less important as the time for vibrational cooling is of the order of picoseconds.