Characterization of the I2 2 anion ground state using conventional and femtosecond photoelectron spectroscopy

The X̃ Su 1 state of the I2 2 anion has been fit to a Morse potential using data from two techniques: conventional and femtosecond photoelectron spectroscopy ~FPES!. Conventional photoelectron spectroscopy is used to determine the adiabatic electron affinity of I2 as well as the well depth and equilibrium nuclear geometry of I2 . In the FPES experiment, the pump pulse induces coherent nuclear motion on the ground state of I2 2 by resonant impulsive stimulated Raman scattering ~RISRS!, and the vibrational frequency of the anion is determined from the resulting oscillatory structure in the time-dependent photoelectron spectra. We find the electron affinity ~EA! of I2 to be 2.52460.005 eV, the well depth (De) for I2 2 to be 1.01460.005 eV, the equilibrium internuclear separation (Re) to be 3.20560.005 Å, and the vibrational frequency to be 11062 cm . These values for the I2 2 potential parameters differ significantly from previous results. © 1997 American Institute of Physics. @S0021-9606~97!02743-8#