Search for a 11/2?→3/2+ M 4 transition in141Sm

The electromagnetic decay of the 11/2^{? 141m} Sm is investigated. Internal conversion electron and X-ray-conversion electron coincidence measurements indicate that the state undergoesβ ⁺ and electron capture decay with 99.69% strength and the remaining 0.31% goes to a 174.2±0.3 keVM4 transition. TheK/L conversion electron intensity ratio for the transition is measured to be 1.7±0.4. The energy of the 11/2^? is established at 175.8±0.3 keV above the 1/2⁺ ground state in¹⁴¹Sm. Systematics of theM4 transitions in theN=79 and 81 isotones are discussed.