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Summary form only given. With the combined techniques of pulsed-dye-amplification (PDA) and harmonic generation we generate Fourier-transform limited pulses in the wavelength domain 58-115 nm that allow for high resolution laser spectroscopic studies. Since the PDA runs at the frequency of a narrowband CW laser there is easy access to measure the absolute frequency of the transition. A first example is that of a precision measurement of the 3p/sup 6/-3p/sup 5/4s'[1/2]/sub 1/ resonance in argon at 105 nm. Based on the on-line recording of saturation spectroscopy of I/sub 2/-hyperfine components in the B-X system, the absolute frequency can be determined. We derive a new value for the ionization potential. Also the transition isotope shift on this transition can be measured, even with higher precision, since only relative measurements are required. Work is in progress to investigate isotope shifts and hyperfine structures in various excited levels of krypton and xenon, again with VUV and XUV laser excitation, with the aim of determining accurate values for the ionization potentials.