The decay scheme of the 284.3D144Ce and energy levels and transitions in 144Pr

The decay scheme of the 284.3d 144Ce has been studied with the help of high resolution X-ray Ge(Li) and 32.2 cm3 Ge(Li) detectors and β-γ, γ-γ, coincidence experiments using scintillation and Ge(Li) detectors. The γ-ray energies (intensities) obtained are: 33.622(2.62), 40.892(3.59), 53.432(0.86), 80.106(10.20), 99.963(0.35) and 133.544(100.00). Gamma-rays with energies 43.0, 66.0, 86.5, 91.0, 146.0 and 166.0 reported in the literature have not been observed in the 144Ce decay. The 40.892 keV γ-ray which is very close to the 40.676 keV kβ'1X-ray of Pr has been studied by a careful comparison of high resolution X-ray spectra of the Pr X-rays emitted in the decay of 144Ce with those from the X-ray fluorescence of spectroscopically pure praseodymium sample. The assignment of an isomer (T=6.6+-1.0 m) to 144Pr has been confirmed by producing this activity through the reaction 144Nd(n,p)144Pr with 14 MeV neutrons. (author)