6533b828fe1ef96bd12890d9

RESEARCH PRODUCT

Spectroscopy of 253No and its daughters

subject

description

Abstract New high-statistics data have been obtained on the decay properties of 253 No and its daughters using the reaction 207 Pb( 48 Ca, 2n) 253 No. This was made possible thanks to an improved transmission of fusion–evaporation residues through the VASSILISSA recoil separator and an increased efficiency of the GABRIELA detector setup. The decay schemes of 253 No and 249 Fm have been revisited. The known level scheme of 249 Fm has been confirmed, including a new level at 669 keV excitation energy. The observation of L X-rays in coincidence with the α decay of 249 Fm gives additional support to the ground-state configuration of 1 / 2 + [ 631 ] instead of 5 / 2 + [ 622 ] for 245 Cf. In both 249 Fm and 245 Cf, the interpretation of the data has been checked by comparing experimental α -particle and γ -ray spectra with realistic simulations of the decay cascades and of the interaction of particles and photons in the detectors of GABRIELA. The population of a 0.7 ms isomeric state attributed to 253 No is confirmed by an α -tagged calorimetric measurement and the corresponding γ and electron decay spectra are presented. Possible evidence for more than one isomer is given and a tentative partial decay scheme is discussed in the light of the available experimental data, systematics and theoretical expectations.