Determination of the ratio of 135Cs / 137Cs radioisotopes using resonance ionization mass spectrometry (RIMS) has been evaluated for measurements requiring extreme background suppression characteristics. Single-resonance excitation of Cs 6s 2S1/2 (F = 4) ® 6p 2P3/2 (F¢ = 5) with an extended cavity diode laser was followed by photoionization with the 488 nm line of an argon ion laser. While the principal objective was to avoid isobaric interferences, an optical selectivity of ~ 3 orders of magnitude against stable 133Cs was attained for both 135Cs and 137Cs. The overall RIMS efficiency was found to be ~ 2´10-6 with a combined (mass spectrometer and laser) selectivity of ~ 1010. The performance with respect to efficiency, selectivity, and isobar suppression has been compared to conventional thermal ionization mass spectrometry (TIMS). Measurements to determine the chronological age of a burn-up sample have been performed using both methods.
Revised: November 7, 2008 |
Published: January 1, 2001
Citation
Pibida L., W. Nortershauser, J. Hutchinson, and B.A. Bushaw. 2001.Evaluation of Resonance Ionization Mass Spectrometry for the Determination of 135Cs / 137Cs Isotope Ratios in Low-Level Samples.Radiochimica Acta 89.PNNL-SA-33551.