Measurements are reported for the absorption of the 422.7 nm line of a natural-abundance calcium hollow cathode lamp by solutions of 40Ca, 44Ca, and 48Ca at 0.5 to 3.0 ppm levels in 0.06 M HCl (aqueous) when aspirated into air-acetylene and nitrous
oxide-acetylene flames. In the case of the air-acetylene flame the relative absorptions per mole of calcium in solution were 1.00, 1.11, and 1.08 for the 40, 44, and 48 isotopes, respectively. With the nitrous oxide-acetylene flame similar experiments gave ratios of 1.00, 1.08, and 1.06 in
the same order. These results may be rationalized with a model that considers the simultaneous effects of isotope shifting, Lorentz broadening and shifting, and Doppler broadening of the calcium resonance line in the flame. With the air-acetylene flame, solutions that also contained 5000 ppm
of Sr as SrCl2 gave relative absorbances for the 40, 44, and 48 calcium isotopes of 1.00, 1.04, and 1.10. Flame-atomic-distribution studies lead to the conclusion that in the presence of 5000 ppm of Sr, calcium kinetic isotope effects are also important.
Department of Chemistry, University of California, Davis, California 95616 2:
Radiobiology Laboratory, University of California, Davis, California 95616
Publication date: September 1, 1979
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