Photodetachment photoelectron spectroscopy of doubly charged anions: S2O82-

A photodetachment photoelectron spectroscopy study of a doubly charged anio n (S2O82-) in the gas phase is reported at three photon energies: 193, 266, 355 nm. Adiabatic and vertical electron binding energies of S2O82- were me asured to be 1.7+/-0.2 and 2.2+/-0.1 eV, respectively. Several excited stat es were observed for the S2O8- singly charged anion at 193 nm. The repulsiv e Coulomb barrier that binds multiply charged anions was clearly shown in t he detachment spectra of S2O82-. The effects of the Coulomb barrier to the detachment spectra and electron tunneling through the barrier are presented . The barrier height, which is equivalent to the magnitude of the Coulomb r epulsion between the two excess charges in S2O82- was estimated to be simil ar to 3 eV. (C) 1999 American Institute of Physics. [S0021-9606(99)02208-4] .