Ultra-trace isotopic analysis by double-resonance ionization spectroscopy

Lasers have unique properties that may be used to improve both sensitivity and selectivity in analytical measurements. Pacific Northwest Laboratory is developing a number of laser-based methods for the measurement and identification of trace levels of radionuclides and environmentally hazardous materials. Over the last year we have improved the techniques of continuous-wave double-resonance ionization mass spectrometry, increasing both sensitivity and selectivity in the spectroscopic process to the point where it may be considered a near ideal atom counter, providing ionization efficiencies approaching unity and isotopic abundance sensitivities in excess of 1010. With completion of the excitation process development, we have shifted emphasis in the program from spectroscopic studies to the development of methodologies for the analysis of small discrete samples. A miniature graphite furnace has been incorporated into the system for the atomization of solid and aqueous samples. Using this furnace, instrumental detection limits of 10-17 grams have been demonstrated for rare isotopes of barium