TRIPLE PHOTOIONIZATION OF LITHIUM

Triple photoionization of an atomic three-electron system has been obs erved for the first time. Triply charged lithium (''bare lithium'') wa s found in the photoion spectrum following synchrotron irradiation of neutral Li vapor. Sequential decay processes, which must result in at least one remaining bound electron, cannot account for such triple ion ization. We have measured the triple-to-single photoionization ratio b etween 187 and 424 eV and made the first, rough estimate for this rati o. The measured triple-photoionization cross section never exceeds 6 b .