(d)  ZEKE spectroscopic studies of Hydroquinone-water complex:

    Using the ZEKE photoelectron spectroscopy following new information was obtained.  Hydroquinone (HQ) exists as the cis and trans isomer.  The ionization potentials of the cis and trans isomers and their water complexes were determined as 64055, 64008, 60024, and 60070 cm-1, respectively.  This suggests that the stability of the water complexes increases by as much as 4000 cm-1 in the cationic state relative to the neutral ground state. This was also evidenced as a long progression in the H-bonding stretching vibration in the ZEKE spectrum. The differences in the Franck-Condon activity of the ZEKE spectra of the two monomeric isomers was exploited to unambiguously establish the correct assignments of the S1-S0 spectrum; the transitions at 33175 cm-1 and 33209 cm-1 were assigned to the cis and trans HQ-water complexes.