Shape-changing particle decays ofBi185and structure of the lightest odd-mass Bi isotopes

Abstract

Proton and ␣ decay of the proton-rich nuclide 185 Bi has been restudied in more detail in the complete fusion reaction 93 Nb͑ 95 Mo, 3n͒ 185 Bi at the velocity filter SHIP. The observed decay pattern of 185 Bi and of the heavier odd-mass isotopes 187,189,191,193 Bi are interpreted based on potential-energy surface calculations. It is shown that the experimental systematics of the particle decays and of the excited states in these nuclei (where known) can be explained by the prolate-oblate shape co-existence at low excitation energy. The observed state in 185 Bi is proposed to be of prolate nature, which is in contrast with the previously proposed oblate interpretation.

Decay of201–203Raand200–202Fr

“…It has also been suggested that this ground state coexists with states related to a proton excitation to the i 13/2 orbital or a proton hole in the s 1/2 orbital, giving rise to an oblate deformation (e.g., Ref. [6]). …”

Experimental study of isomeric intruder 12+ states in At197,203

“…For the first time we have observed the isomeric intruder 1 [4], and later Andgren et al [32] saw the first γ -ray transitions feeding the 1 /2 + state. In Fig.…”

“…If this is the case then the kinematic moment of inertia (1) can be extracted and compared to the kinematic moments of inertia of other cascades in neighboring nuclei. This is shown as a function of rotational frequency ω in Fig.…”

“…Our recent study [5] presented the level structures above the 1 /2 + states in 199,201 At. Similarly to heavier bismuth isotopes, the two lowest levels above the 1 and those were suggested to originate from the π (d3 /2 ) −1 and π (d5 /2 ) −1 configurations, respectively. In this publication we present the feeding and depopulation of the isomeric intruder 1 /2 + state in 203 At.…”

“…In bismuth nuclei this state is well known. The level energy is pushed down as the neutron number decreases, and it becomes the ground state in 185 Bi ( [1], and references therein). In odd-mass astatine nuclei this state is known in isotopes [191][192][193][194][195][196][197][198][199][200][201] At [2][3][4][5].…”