Nuclear structure of $$^{181}$$Au studied via $$\upbeta ^+$$/EC decay of $$^{181}$$Hg at ISOLDE

Abstract

The β + /EC decay of mass separated samples of 181 Hg was studied employing the TATRA spectrometer at the ISOLDE facility at CERN. The decay scheme was constructed for the first time. A Broad Energy Germanium detector was used to achieve this by combination of high-gain γ-ray singles spectroscopy and γ-γ coincidences. The systematics of excited states associated with the 1h 11/2 proton-hole configuration in odd-Au isotopes was extended.

Identification of sub- μs isomeric states in the odd-odd nucleus Au178

“…(a). A value of α tot,exp (50.2) = 26(8) was deduced, which is consistent, within the uncertainty, to the α tot,exp (50.2) = 19.3(25) deduced via the ER-PGD(γ γ ) method in Sec. IV B.…”

“…1(a), but with an additional energy gate of ±1 keV on the 56.7-keV isomeric decay. Two α-decay peaks with energies of 5926 (8) and 5976 (8) keV are seen, which match well to the strongest decays of 178 Au m [18]. Therefore we assign the 373-ns, 56.7-keV transition as feeding to the high-spin α-decaying isomer of 178 Au; see Fig.…”

“…The region surrounding the Z = 82 shell closure is well known for its exhibition of shape coexistence [1]. The neutron-deficient gold (Z = 79) isotopes are one of the earliest examples of this phenomenon, and have been studied by a variety of decay and in-beam nuclear spectroscopy techniques [2][3][4][5][6][7][8][9][10]; see also the recent review [11] and references therein. The ground state of gold nuclei displays a large increase in the mean-squared charge radius when approaching the N = 104 midshell [12,13].…”

“…While the gold isotopes with A > 186 possess weakly oblate ground states, [183][184][185][186] Au are seen to have strong, prolate shapes. This sudden change in ground-state deformation has been related to the presence of π i 13/2 , π h 9/2 , and π f 7/2 intruder states at low energies, alongside spherical π s 1/2 , π d 3/2 , and π h 11/2 configurations [5,7,8]. Rotational bands built on top of these intruder states have been identified in several odd-A isotopes [2,[14][15][16], with an observed parabolic trend in the bandhead energies as a function of neutron number (see for example, Fig.…”

An experimental view on shape coexistence in nuclei

“…64. Recent measurements for 181,183 Au [560,561] provided more data on the variety of normal-order and intruder states in these nuclei. In particular, in 183 Au an E0 transition feeding the first 3/2 − state of the 2d 3/2 ⊗ 3s 1/2 proton-hole configuration was reported in Ref.…”