Photodissociation of (C6H6)2 + is studied with photon energies between 1.29 and 2.81 eV. Massselected ion beam of (C6H6)2 + is photodissociated by a pulsed laser beam in the field-free region of a reflectron-type time-of-flight mass spectrometer. The average relative translational energy, 〈εt〉, and the angular distributions of the photofragments (C6H6 + and C6H 6) are measured as a function of photon energy. With a photon energy of 2.81 eV, the (C6H6)2 + ions are promoted to a bound upper state correlated to C6H6 +(ππ) + C6H6(X). Only a small fraction (≈3%) of the available energy is partitioned into the translational energy of the fragments and the product angular distribution is isotropic. Absorption of a photon in the range of 1.29-2.14 eV induces a charge resonance transition to a repulsive upper state which correlates to C6H6 +(X) + C6H6(X). The observed values for 〈εt〉 are at most 10% of the available energy, although the statistical phase space calculation shows that the complete randomization of the available energy is not achieved. As the photoexcited (C 6H6)2 + moves apart on the dissociative potential surface, ≈90% of the available energy flows into the intramolecular modes of the fragments. The energy partitioning becomes almost statistical regardless of the photoexcitation to a dissociative state.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry