Isomeric E1 and M1 transitions in 177Ta and in neighbouring odd- A Lu and Ta isotopes

Abstract

Delayed γ-ray spectra as well as time distributions have been measured applying the r.f.-γ method and the method of delayed γ-γ coincidences. Using the reaction 175Lu(α, 2n) 177Ta, the half-lives of the levels at 70.6 and 73.6 keV in 177Ta have been determined as T 1 2 = 80±10 ns and T 1 2 = 370±50 ns , respectively. In further experiments, upper limits for the lifetimes of the 9 2 − [514] and 5 2 + [402] states in 171Lu and 173Lu were estimated. Comparisons of the experimental half-lives to Weisskopf and Nilsson model predictions are performed taking into account pairing correlations. For the calculations, a modified Nilsson Hamiltonian has been used. The hindrance factors obtained are summarized together with those deduced for corresponding transitions in neighbouring odd-proton nuclei. From the experimental results in 177Ta, conclusions have been drawn on the possible value of the constant k 2 occurring in the magnetic dipole operator.