Springer Online Journal Archives 1860-2000
Abstract An isomeric state of Hf177 withT 1/2=(1,12±0,10)s was found by a fast chemical separation of the hafnium daughter from the 155d Lu177m activity. We measured the same half-life by observing the delayedβ-γ-coincidences. A systematic investigation of the whole region 5s≧T 1/2≧10−7s by the technique of delayed coincidences gave no further isomerism. We assign the observed half-life to the 23/2 three particle state of Hf177 at 1315 keV and assume that the second hypothetical three particle state at 1337 keV does not exist. The 21/2 rotational state of theK=9/2 band is populated by a strongly converted 14,16 keVγ-transition from the isomeric state at 1315 keV. The 14,16 keVM I andN I conversion lines were observed by use of a double focusing magneticβ-spectrometer. The isomerism is caused by theK-selection rule. The retardation of the following threeγ-transitions by different degrees ofK-forbiddeness is discussed. The pulse height spectrum, measured by means of a Li-drifted Ge-detector, does not show the 36,52 keV-γ-transition which was previously assumed to populate the 1301keV-state. In addition to the knownγ-transitions we found a 40,9 keV-line. This is probably the transition between the 1301,1 keV and the 1260,3 keV-states.
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