Time-Resolved Photodissociation (TRPD) of the Naphthalene and Azulene Cations in an Ion Trap/Reflectron

Dissociation rates have been measured by multiphoton ionization and time-resolved photodissociation for benzene-d 6 •+, naphthalene-h 8 •+, naphthalene-d 8 •+, and azulene-h 8 •+ employing a quadrupole ion trap/reflectron mass spectrometer. Results compare favorably with available data from ICR cells and cylindrical ion traps. Azulene•+ is photodissociated upon absorption of two 400 nm photons giving C2H2, H·, and H2 eliminations. Dissociation rate constants measured for naphthalene•+ and azulene•+ at identical absolute energies are equal within experimental error. This experimental result is in agreement with previous density functional theory (DFT) calculations that demonstrated the isomerization of azulene•+ to naphthalene•+ below the dissociation limit of benzocyclobutadiene•+ + acetylene.