Erlangen 2026 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 39: Structure and Dynamics of Nuclei VIII

HK 39.3: Vortrag

Donnerstag, 19. März 2026, 16:45–17:00, AM 00.011

In-gas-jet laser ionization spectroscopy of the K = 8⁻ isomer in ²⁵⁴No — •Premaditya Chhetri for the JetRIS collaboration — Johannes Gutenberg Universität, Mainz, Germany

Decay and in-beam spectroscopy have provided extensive information on the level structure of heavy nuclei, but often cannot unambiguously determine the underlying single-particle structure of the nucleus. This limitation is particularly evident for the long-lived K^π = 8⁻ isomer in ²⁵⁴No, whose quasiparticle structure has remained disputed for almost two decades. In fusion-evaporation experiments, the rotational band built of this isomer is only weakly populated preventing a reliable measurement of key observables such as M1/E2 branching ratios and g-factors. Consequently, previous configuration assignments mainly relied on indirect decay patterns and comparisons with nuclear models.

Here, we report on in-gas-jet laser ionization spectroscopy measurements of the K = 8⁻ isomer in ²⁵⁴No performed with the JetRIS setup at the SHIP velocity filter at GSI. After stopping and neutralization in argon gas, the atoms are re-ionized in a supersonic gas jet using a two-step laser ionization scheme. The resulting hyperfine structure provides direct, nuclear-model-independent access to the magnetic dipole moment, electric quadrupole moment, and isomer shift of the K = 8⁻ state. The deduced intrinsic g-factor allowed an unambiguous assignment of configuration of the isomer, resolving a long-standing ambiguity in the nuclear structure of ²⁵⁴No.

Keywords: Nobelium; Isomer; Laser ionisation spectroscopy