NASCENT VIBRATIONAL DISTRIBUTION OF THE O-2(-) PRODUCT ION IN THE PHOTODISSOCIATION OF (O-2)N(-), N = 2-4

The nascent vibrational distributions of the O2- photoproduct created in the processes (O2)n- + h-nu --> O2-(nu) + (n - 1)O2 are obtained at 1.165 and 2.33 eV by analyzing the photoelectron spectrum of the O2- fragment ions. The distributions at 1.165 eV reveal substantial population in the levels 0 less-than-or-equal-to- upsilon less-than-or-equal-to 3 and are reasonably well characterized by Boltzmann distributions with temperatures of 2600 and 1500 K for n = 3 and 4, respectively. The average O2- vibrational energy decreases from 0.11 +/- 0.01 to 0.065 +/- 0.005 eV in going from n = 3 to n = 4, representing a cooling of about half of the binding energy associated with the fourth O2. The cooling of the monomer photofragment is correlated with the onset of dimer formation for n > 3.