Thermal vaporization resonance ionization mass spectrometry

The combination of the ionization efficiency and elemental selectivity of resonance ionization spectroscopy with the isotopic discrimination of mass spectrometry is known as resonance ionization mass spectrometry or RIMS. Much of the normal gestation period of any new analytical method can be circumvented by combining the new laser-ionization source with the time-tested technology of thermal ionization isotope-dilution mass spectrometry (IDMS). Use of a pulsed frequency-doubled tunable laser system provides broad access across the periodic table, with only infrequent (predictable and correctable) isotopic bias in the ionization process. The pulsed ionization process causes some unique disadvantages due to the duty factor mismatch with the continuous vaporization source and the upper limit on the number of ions resulting from space charge and multiplier linearity effects. On the other hand, the temporal definition of the signal yields valuable time-of-flight mass discrimination convoluted with the magnetic dispersion. The capabilities and shortcomings of thermal vaporization RIMS and plans for future improvements are discussed.