First observation of high- K isomeric states in ^249 Md and ^251 Md

Decay spectroscopy of the odd-proton nuclei ^249 Md and ^251 Md has been performed. High- K isomeric states were identified for the first time in these two nuclei through the measurement of their electromagnetic decay. An isomeric state with a half-life of 2.8(5) ms and an excitation energy ≥ 910 keV was found in ^249 Md. In ^251 Md, an isomeric state with a half-life of 1.4(3) s and an excitation energy ≥ 844 keV was found. Similarly to the neighbouring ^255 Lr, these two isomeric states are interpreted as 3 quasi-particle high- K states and compared to new theoretical calculations. Excited nuclear configurations were calculated within two scenarios: via blocking nuclear states located in proximity to the Fermi surface or/and using the quasiparticle Bardeen–Cooper–Schrieffer method. Relevant states were selected on the basis of the microscopic-macroscopic model with a deformed Woods–Saxon potential. The most probable candidates for the configurations of K -isomeric states in Md nuclei are proposed.