Electric field effects on the lifetimes of states detected in zero electron kinetic energy experiments

Lifetime measurements are reported for zero-electron-kinetic-energy (ZEKE) states of benzene, using a novel technique which measures relative intensity losses tens of microseconds after laser excitation. The influence of electric fields on the measured lifetimes, present during laser excitation and present through delayed pulsed field ionization, were investigated. It is demonstrated that the presence or the absence of an electric field during laser excitation has a dramatic effect on the formation of ZEKE states, however, has no measurable effect on their late time (12-24 mu s) decay rates. It is also demonstrated that the presence of an electric field, applied after laser excitation and through delayed pulsed field ionization, leads to a significant enhancement in the late time component of the ZEKE state lifetime. Lifetime measurements repeated on deuterobenzene were found to be identical to those determined for benzene, suggesting the absence of any isotope effects.