ISOTOPE RATIO MEASUREMENTS IN LEAD USING 3-PHOTON ONE-COLOR RESONANCEIONIZATION MASS-SPECTROMETRY

Resonance effects on measured isotope ratios in lead using three-photo n one-colour resonance ionization mass spectrometry are discussed. The shape of the ionization signal is considered for the case of a non-mo nochromatic laser field. The intensity of the laser radiation is adjus ted to be low enough not to cause saturation of the transitions. The v ariation of the measured isotope ratio as a function of laser frequenc y is considered. It is shown that the deviation of the measured from t he expected isotope ratio, for a Lorentzian laser lineshape equals the ratio of the isotope shift to the laser bandwidth. Unfortunately, the background noise in the experiments makes verification of this behavi our difficult for the isotopes of low abundance.