ZERO-KINETIC-ENERGY PHOTOELECTRON-SPECTROSCOPY AND EXCITED-STATE INTRAMOLECULAR PROTON-TRANSFER IN A DOUBLE BENZOXAZOLE

Resonant two-color photoionization spectroscopy has been used for the first time to study rt compound which exhibits an enol --> keto reacti on after electronic excitation. Detecting only photoelectrons with zer o kinetic energy (ZEKE), we observe two energy thresholds for ionizati on from selected vibronic levels of the jet-cooled molecule. The thres holds are assigned to the excited enol and keto forms. The implication s for the ultrafast time-resolved spectroscopy of the reaction are dis cussed.