Alpha-decay study of188Pb and180,182Hg

Abstract

The e decay of mass-separated 18Spb and 18~has been studied at the GSI on-line mass separator. Alpha singles spectra as well as a :-X -t and e-e -t coincidence events were collected. Fine structure in the e decay of 188pb was measured for the first time, feeding the 2 + and 0~-states in 184Hg. The e decay of ~8~ feeds low-lying states in 176'178pt. One of these states could be identified as a 0 + state. The deexcitation pattern could be established. As a by-product an alpha-decay scheme of 18~ towards levels in 176Ir is given. The experimentThe 188pb and 18o, 182Hg isotopes were produced at the GSI mass-separator facility at Darmstadt, in the following fusion-evaporation reactions:

Alpha decay ofPb186andHgWauters1, Bijnens2, Folger3 et al. 1994Phys. Rev. CSelf Cite605570View full textAdd to dashboardCite

“…At the very neutron-de6cient side, namely between 6Pt and Pt, the level systematics indicate that the strongly deformed band rises again in energy with decreasing neutron number [1]. From our a-decay studies of isoHg and Hg, the variation of the hindrance factor for the o. decay towards the excited 0+ state (17 and 3.5, respectively) supports this configuration change between Pt and i"sPt [3]. Closer to midshell, at isoPt, the mixing in the ground state of the strongly deformed states with the normal states is believed to be even larger than for Pt.…”

“…The resulting excitation energy, 338 keV, lies within the uncertainty on our experimental value [328 (12) keV]. Taking into account an uncertainty of 20 keV on the estimated excitation energy of the deformed bandhead, one obtains a xxxxxing probability of & 4% between the ground state and the 02+ state of i Hg, similar to i Hg [3]: & 3%. Lifetime measurements of the excited 0+ state in F86,&88Hg have been performed at UNISOR [12].…”

“…[3] make it now possible to discuss in a coherent way the large variation (from 2.4 to 21) in the hindrance factor of the n decay towards the excited state relative to the decay towards the ground state. Three states are connected in these decay studies: the ground state of the parent nucleus, the excited 0+ state in the daughter nucleus, and the ground state in the daughter nucleus.…”

“…The hindrance factor for the n decay towards the 02+ state is 2.4(2). Figure 4 shows the a-decay scheme of~s 4Hg, together with the a-decay schemes of Hg, taken from [3]. …”

“…[2]. Recently, we studied the a decay of Pb, feeding the 02+ state at 375 keV, and the 2y state at 367 keV [3]. The large hindrance factor (HF=21) of the o. decay towards the 02 state relative to the n decay to the ground state indicates that the 02+ state might be based on a vr(2p-4h) (two-particle -four-hole) configuration, giving a strong retardation of the a decay of the Pb m(0p-Oh) ground state towards this state, compared to the a decay towards the vr(2h) ground state [2,3].…”