Abstract
The electron capture decays of133Ba (10.4 y) and139Ce (140 d) were investigated with high resolution Ge(Li) detectors. By x-ray — γ-ray coincidences values of the quantityP k ω k ɛ k for various transitions in the decay of133Ba and139Ce are obtained. The factor ω k ɛ k was measured independently by means ofK-conversion electron-K x-ray coincidences and was then used to determineP k , theK-capture probability. The independent measurement of the product ω k ɛ k , together with recent accurate values of ω k , provides a new method for the accurate calibration of semiconductor x-ray detectors. In the decay of139Ce, a value ofP k =0.78±0.03 is found (where the error represents twice the standard deviation) from whichQ ec =326 +70−30 keV to the139La ground-state is found by use of theory. In133Ba decay, values are found ofP k 1=0.72±0.04 for theEC transition to the 437 keV level in133Cs,P k 2=0.80±0.07 to the 384 keV level, and from an independent measurement, the ratioP k 1/P k 2=0.87±0.07. From these results the ground-state value ofQ ec =522 +20−10 keV is derived from theory for133Ba decay. The gamma spectrum of133Ba also was remeasured. From the present gamma intensities and previous conversion electron intensities, new values forK-shell conversion coefficients are obtained. Previously reported γ-rays at 35 and 391 keV are not confirmed.
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Supported in part by the U. S. Atomic Energy Commission.
On leave from University of Göttingen.
We should like to thank Dr. J. C. McGeorge and Dr. J. S. Hansen of the Georgia Tech School of Chemistry suggesting the conversion electron coincidence measurements.
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Schmidt-Ott, W.D., Fink, R.W. The determination by an independent method ofP k electron capture probabilities in133Ba and139Ce decays gamma decay of133Ba. Z. Physik 249, 286–293 (1972). https://doi.org/10.1007/BF01379722
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DOI: https://doi.org/10.1007/BF01379722