RESONANCE-ENHANCED 2-PHOTON IONIZATION OF HE AND XE USING A MODE-LOCKED AR-RADIATION PULSES( LASER SYNCHRONIZED TO VUV SYNCHROTRON)

The light pulses of a mode-locked Ar+ laser have been synchronized to the synchrotron radiation pulses of the SuperACO storage ring in Orsay . In order to test the feasibility and to demonstrate the capability f or the investigation of free atoms we have studied the two-photon ioni zation of atomic Helium and Xenon via the He 1s3p and Xe* 5p(5)5d res onant state, respectively. The experimental results show clearly an io nization signal which strongly depends on the temporal delay between t he two light pulses. The spectra can be interpreted as the convolution of an exponential function representing the lifetime of the intermedi ate resonant state and a Gaussian function representing the cross corr elation function of the synchrotron and laser radiation. The overall t ime resolution of the present set-up has been estimated to about 1ns.