ZEKE-PFI spectroscopy of 1:1 complexes of sodium with water and ammonia

ZEKE-PFI (zero kinetic energy pulsed field ionization) photoelectron spectra of the Na(H2O), Na(D2O), Na(NH3), and Na(ND3) complexes are reported. Spectra of all four complexes were obtained by single-photon ionization, and, for the Na(NH3) and Na(ND3) complexes, by two-color (1 + 1′) photoionization as well, with the Ã2E state serving as the intermediate resonance. Improved values for the ionization energies (IE) and intermolecular vibrational frequencies of the complexes were determined. The single-photon ZEKE-PFI spectra show transitions only between states of the same vibrational symmetry, in accord with the selection rule for allowed electronic transitions. Some of the two-color ZEKE-PFI spectra, however, show strong transitions between states of different vibrational symmetry which we attribute to vibronic coupling in the intermediate state.