Possible evidence for shape isomeric γ-decay in μ− atoms of 238U

Abstract A search for the γ-decay of the shape isomer in muonic 238 U excited by radiationless transitions has been performed. Seven delayed transitions in the energy region of 700 to 3200 keV have been observed with a large Ge(Li) detector. Two transitions with E γ = 2215 and 3131 keV have been attributed to the decay of the shape isomeric state into levels in the first well. The isomeric shift of the second minimum E 11 ≈ 600 keV in the presence of the muon and the decrease of the lifetime of the shape isomer to τ = 12 ± 2 ns give arguments in favour of the connection of shape isomerism with large quadrupole deformations.