Search for μs-isomers in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"> <mml:msup> <mml:mrow/> <mml:mrow> <mml:mn>251</mml:mn> <mml:mo>−</mml:mo> <mml:mn>254</mml:mn> </mml:mrow> </mml:msup> </mml:math> No

Nuclear isomers are one of the main probes for exploring the underlying nuclear structure. In heavy nuclei, especially in nobelium isotopes, many isomers are known and have been intensively studied both experimentally and theoretically. This revealed their shell structure, which primarily defines stabilities of the heaviest nuclei against spontaneous fission. In the present work, we revisited the isotopes 251 − 254 No and their daughters by searching for hitherto unknown isomers with half-lives on the order of μ s using the fast digital electronics. In 253 No and 254 No, we did not find evidence for new μ s-isomers. In 251 No, we observed the isomeric state with a half-life of 4 − 2 + 6 μ s, which confirms the previously reported ≈ 2 μ s-isomer. In 252 No, we observed evidence for the presence of a new 9 − 4 + 13 μ s isomeric state, in addition to the known 110 ms two-quasiparticle K -isomer.