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Abstract

The β decay Cs134 → Ba134 has been investigated with a double focusing β-ray spectrometer and a β-γ circular-polarization correlation setup. The asymmetry parameter A of the correlation between the 656 keV β group and the following γ cascade was measured to be A = −0.13 → 0.02, in good agreement with a very recent value of Mann, Bloom, and Nagel. This A value implies a ratio X between Fermi and Gamow-Teller contributions to the decay of X = 0.30 ± math image and so a definitely nonvanishing Fermi matrix element. The breakdown of the isotopic spin selection rule at an atomic number as large as that of Cs(Z = 55) is not surprising. The β transition is qualitatively discussed in shell model terms. Additional information is given for the disintegration scheme of Cs134. The level scheme of Ba134 is discussed in terms of the vibrational model.