Stability ofS50100n50Deduced from Excited States in

M. Lipoglavšek¹,

J. Cederkäll²,

M. Palacz³

et al.

Abstract

Excited states of neutron deficient nuclei close to 100 Sn were investigated in an in-beam spectroscopic experiment using the NORDBALL detector array. Excited states in 99 Cd were identified for the first time. The measured half-life of an isomeric state in 99 Cd indicates that the stability with respect to quadrupole shape changes is as large in 100 Sn as for other heavy doubly magic nuclei. PACS numbers: 23.20.Lv, 21.10.Tg, 25.70.Gh, 27.60.+j The region of nuclei near 100 Sn has recently come in focus for studies of nuclear structure. The reason is that 100 Sn is the heaviest N Z nucleus, which may show strong shell closure and is accessible to experimental investigations. A handful of 100 Sn ions have recently been observed in two experiments [1,2], and excited states have been identified in neighboring nuclei, e.g., 97 Ag [3], 98 Ag [4], 100 Cd [5], 102 In [6], and 104 Sn [7]. In this work we report on the observation of excited states in the nucleus 99 48 Cd 51 , which has two proton holes and one neutron outside the 100 Sn core and is now, together with 97 Ag, the closest neighbor to 100 Sn with known excited states.An important property of 100 Sn is the degree of rigidity of its spherical equilibrium shape. This is directly related to the excitation energy and transition rates of the lowest 2 1 state. The main wave function component of this state in a microscopic description is an isoscalar mixture of proton and neutron excitations 2d 5͞2 1g 21 9͞2 across the N Z 50 shell closures. This 2 1 1 state will be lowered in energy and its collective strength increased by coupling to the high-lying giant quadrupole vibrations.The excitation energy and collectivity of the 2 1 1 state in 100 Sn are not known from experiment. In the heavy closed-shell nuclei 132 Sn and 208 Pb, the excitation energies of the 2 1 1 states are 4.04 and 4.09 MeV, respectively, while it is 2.70 MeV in the light N Z doubly magic 56 Ni. The splittings of the relevant single particle states 2p 3͞2 1f 7͞2 ( 56 Ni, 6.40 MeV), 2d 5͞2 1g 9͞2 ( 100 Sn, ഠ6 MeV [8]), 2f 7͞2 1h 11͞2 ( 132 Sn, 4.90 MeV), and 2g 9͞2 1i 13͞2 ( 208 Pb, 5.07 MeV) are comparable. Since the lowering by the proton-neutron interaction should be particularly effective when the protons and neutrons occupy identical quantum states, it is not unlikely that, as in 56 Ni, the 2 1 1 state comes lower in 100 Sn than in 132 Sn or 208 Pb. A B͑E2, 2 1 ! 0 1 ͒ 9͑2͒ W.u. was recently measured in 56 Ni [9]. As a consequence, the polarization charges for low energy E2 transitions in the neighborhood of 100 Sn could be enhanced. There is experimental evidence [8] from B͑E2, 6 1 1 ! 4 1 1 ͒ values in light Sn isotopes down to 104 Sn which points to a neutron effective charge of more than 2e, i.e., about twice as large as the values in the 132 Sn and 208 Pb regions. However, the analysis of the Sn transition rates is troubled by the difficulty to fix the amount of configuration mixing in the initial and final states. We will show below that the present experiment provides independent and...

Spectroscopy of Cd99 and In101 from β decays of Park1, Krücken2, Blazhev3 et al. 2020Phys. Rev. CSelf Cite

“…The amount of knowledge on excited state(s) varies widely among the different nuclei. state in 99 Cd has been found to be 441 keV above the (5/2 + ) ground state [8], supplementing the first spectroscopy results for this nucleus [9]. On the other hand, the energy gap of the two states in 101 Sn was first measured to be 172 keV [10] but without a clear consensus on the order of the two spins for 101 Sn [11][12][13].…”

“…Experimental (black) and theoretical (blue and red) β-delayed γ -ray intensities in 99 Cd. The initial-final spin labels are taken from SM calculations, and the dashed lines and ellipses help guide the reader the matching transitions where tentative spins were previously assigned [8,9]. motivated by the SM results.…”