Levels in ¹⁵⁴Eu populated by (n, γ) and (d, p) reactions

The structure of the doubly-odd nucleus ¹⁵⁴Eu was investigated using neutron capture and (d, p) reactions on ¹⁵³Eu. The low-energy γ-ray and conversion electron spectra from thermal neutron capture, as well as the γ-ray spectrum for primary energies up to 6.5 MeV, were measured with precision instruments at the Institut Laue-Langevin, Grenoble. The multipolarities were determined for most of the detected low-energy transitions. The (n_res, γ_high) spectrum measurements with 2 keV, 2 eV and 3 eV neutrons were performed at Brookhaven National Laboratory for primary transitions leading to the 0-600 keV excitation energies. The ¹⁵³Eu(d, p)¹⁵⁴Eu reaction was measured with the Q3D spectrograph at TU Munich. A level scheme below 600 keV excitation energy comprising 99 levels was deduced and the parities and most probable spin values were determined from the experimental data. The low-lying levels were interpreted as due to the two-particle Nilsson configurations, taking into account the proton orbits 5 2⁺[413], 5 2^-[532], 3 2⁺[411], and the neutron orbits 11 2^-[505], 3 2⁺[651], 3 2^-[521], 3 2^-[532], 5 2⁺[642], 3 2⁺[402], 5 2^-[523], 1 2⁺[400], 1 2^-[530]. The 145.3 (± 0.3) keV level observed in the (d, p) reaction can be identified with the isomeric level with T _{1 2} = 46 min. The neutron separation energy for ¹⁵⁴Eu was determined to be 6442.0 ± 0.3 keV.