| Research Abstract |
A new apparatus of two-color zero-kinetic-energy (ZEKE) photoelectron spectrometer with a compact, high-resolution, high-brightness ZEKE electronanalyzer earlier developedin our group, has been set up at the Japan Advanced Institute of Science and Technology here at Tatsunokuchi since 1993. The energy resolution has been further improved by introducing a "two-pulsed-field" technique in our AEKE photo-electron measurements, and this technique has been successfully applied to our MATI (Mass Analyzed Threshold Ionization Spectroscopy).
In the two-color ZEKE measurements, two ns lasers are used, one is for excitation to a specific excited state, and the other is for further excitation to very high Rydberg states just a few wavenumber below the ionization threshold. In order to carry out measurements of very high resolution ZEKE electrons (less than one wavenumber), we have applied two kinds of pulsed electricfields with an appropriatedelay time, one is to remove all the emitted photoelectrons as well as some very shallow Rydberg electrons, and the other is to collect somewhat deeper Rydberg electrons.
The molecules studied in the present work are some benzene derivatives and higher aromatic molecules (benzonitrile, fluorobenzene, thioanisole, tetrafluorobenzene, naphthalene, indole, etc.) and their van der Waals complexes mainly with argon in supersonic jets. As results, we have successfully determined the adiabatic ionization potentials of these molecular species including van der Waals complexes formedin jets. We have also been able to observe van der Waals vibrational frequencies of the van der Waals cations from ZEKE photoelectron spectra.
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