Absolute Transition Probabilities in the Odd-Odd NucleusPr144

Abstract

The lifetimes of three levels of the odd-odd ${\mathrm{Pr}}^{144}$ nucleus were determined by coincidence measurements between the beta spectrum of ${\mathrm{Ce}}^{144}$ and the conversion lines de-exciting the levels under investigation, using a double-lens coincidence spectrometer. The measurements were carried out using both the conventional self-comparison method and a modified version of this technique particularly appropriate for low-energy transitions. The mean lifetimes of the 133.5-, 100-, and 80.1-keV levels were found to be: (0.95\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}11}$ sec, (1.0\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}9}$ sec, and (1.8\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}10}$ sec, respectively. The transition probabilities agree very well with those derived from shell model calculations in terms of coupling between the odd neutron and odd proton, if values of the "effective moments" are used in the calculation.The following assignments for the unpaired neutron-proton configurations provide a consistent description of the states: Ground state: $|{f}_{\frac{7}{2}}, {g}_{\frac{7}{2}}; 0\ensuremath{-}〉.$ 80-keV Level: $0.37|{f}_{\frac{7}{2}}, {g}_{\frac{7}{2}}; 1\ensuremath{-}〉+0.93|{f}_{\frac{7}{2}}, {d}_{\frac{5}{2}}; 1\ensuremath{-}〉.$ 100-keV Level: $|{f}_{\frac{7}{2}}, {g}_{\frac{7}{2}}; 2\ensuremath{-}〉.$ 133-keV Level: $\ensuremath{-}0.93|{f}_{\frac{7}{2}}, {g}_{\frac{7}{2}}; 1\ensuremath{-}〉+0.37|{f}_{\frac{7}{2}}, {d}_{\frac{5}{2}}; 1\ensuremath{-}〉.$