Detailed spectroscopy in $^{249}$Fm

A. Lopez-Martens (1) , K. Hauschild (1) , A.V. Yeremin , A.V. Belozerov , C. Briançon (1) , V.I. Chepigin , D. Curien (2) , O. Dorvaux (2) , B. Gall (2) , V.A. Gorshkov , M. Guttormsen , F. Hanappe , A.P. Kabachenko , F. Khalfallah (2) , A. Korichi (1) , A.C. Larsen , O. N. Malyshev , A. Minkova , Yu. Ts. Oganessian , A.G. Popeko , Marc Rousseau (2) , N. Rowley (2) , R.N. Sagaidak , S. Sharo , A.V. Shutov , S. Siem , A.I. Svirikhin , N.U.H. Syed , C. Theisen (3)

1 CSNSM - Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse
2 DRS-IPHC - Département Recherches Subatomiques
3 DAPNIA - Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée

Excited states in 249Fm were populated via the alpha decay of 253No and the subsequent decay was observed with the GABRIELA detection system installed at the focal plane of the VASSILISSA recoil separator. The energies, spins, and parities of these states could be established through combined alpha, gamma, and conversion-electron spectroscopy. The first members of the ground-state rotational band were identified. Their excitation energies as well as the observation of a cross-over E2 transition confirm the assignment of 7/2+[624] for the ground state of 249Fm. Two excited states were also observed and their decay properties suggest that they correspond to the particle excitation 9/2-[734] and hole excitation 5/2+[622]. The analysis suggests that the 279-keV transition de-exciting the 9/2- state has anomalous E1 conversion coefficients.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

A. Lopez-Martens, K. Hauschild, A.V. Yeremin, A.V. Belozerov, C. Briançon, et al.. Detailed spectroscopy in $^{249}$Fm. Physical Review C, 2006, 74, pp.044303. ⟨10.1103/PhysRevC.74.044303⟩. ⟨hal-00104695⟩