Intrinsic Excited States inHf178Populated by the Allowed Decay of 9.3-minTa178

Abstract

The levels in ${\mathrm{Hf}}^{178}$ populated by the allowed positron and electron capture decay of 9.3-min ${\mathrm{Ta}}^{178}$ have been investigated with the Copenhagen six-gap spectrometer. Conversion-electron spectrum and beta-gamma coincidence measurements have established the spin and parities of levels in ${\mathrm{Hf}}^{178}$ with energies (in kev) 93(2+), 307(4+), 1197(0+), 1277((2+)), 1430((1+)), 1440(0+), and 1483(2+), and possibly a level at 1550. (Double parentheses indicate that the spin is not definitely established.) Intrinsic configuration assignments for the excited states are discussed in terms of recent theoretical developments. The half-life of the 93-kev level has been measured and found to be (1.25±0.08)×${10}^{-9\mathrm{}}$ sec. The $\frac{{\beta }^{+}}{K}$ capture ratio measured for the allowed decay to ground is within experimental error of theory. Reduced $\frac{E0\mathrm{}}{E2\mathrm{}}$ transition probability ratios for the transitions depopulating the 1197- and 1440-kev 0+ levels have been calculated from the observed $K$-conversion line intensities of the $E0\mathrm{}$ and $E2\mathrm{}$ transitions depopulating the levels.