Remarks on the fission barriers of super-heavy nuclei

Abstract

Shell-correction energies determine the stability and the fission barriers of Super-Heavy Nuclei (SHN), the latter being a main factor responsible for their production yield. Although recent experiments performed at FLNR in Dubna (see review articles [1,2]) have confirmed the existence of an island of SHN, the site and strength of highest stability is still uncertain. Predicted Q  values as shown in Fig. 1a reveal the ambiguity. The macroscopic-micro-scopic (MM) models [3,4] predict a closed proton shell at Z = 114 and thus increasing Q  values beyond. The chiral mean-field model (CMF) [5] and the semi-empirical model (SE) [6] predict subshells or shells at 120 and 126, respectively, resulting in less steep or even decreasing Q  values. Experimental data, also shown in Fig. 1a and known up to Z = 116 do not give preference to a specific model. However, decisive information could be obtained from the -decay properties of elements 118 and 120. The following discussion supports our search experiment for element 120. The study also reveals an important uncertainty related to the prediction of cross-sections of the synthesis of SHN. Shell-correction energiesModel dependent experimental shell-correction energies can be deduced from measured nuclear masses by subtraction of theoretically determined liquid-drop masses. In our case, however, absolute experimental nuclear masses are not known, but relative values can be determined for nuclei within an -decay chain using the experimental Q  values. Normalizing these relative masses to the theoretical ones at the end of the decay chain, which is closer to the region of known masses, where relatively good agreement was established [7], results in a reliable approximation of masses up to the heaviest nuclei of the -decay chain. In one case, where a relatively long decay chain starting at 291 Lv and ending at 267 Rf is known, we have performed such an estimate of shell-correction energies. Interestingly, this is the decay chain which would be populated in a 3n channel of the reaction 54 Cr + 248 Cm. In Figs. 1b and 1c, Rf to 279 Ds were normalized by a least squares fit to the theoretical masses. In order to distinguish between the so determined masses, shell-correction energies and fission barriers from the theoretical ones, we denote those 'experimental data' in the following.

Distinct ground state features and the decay chains of Z = 121 superheavy nuclei

“…Up to Z = 118, many superheavy nuclei have been produced either by cold fusion reaction with target 208 Pb and 209 Bi at GSI [1,2] and RIKEN [3] or by hot fusion with projectile 48 Ca at JINR [4,5,6]. For higher Z = 119, 120, few attempts [7,8] have already been made towards exploring the superheavy nuclei. However the scope to explore further and search for distinct features beyond Z > 120 is limitless.…”

Physics of even-even superheavy nuclei with 96<Z<110 in the quark-meson-coupling model

“…These models are widely used in the SHE community and provide a benchmark for a comparison with the QMC calculations. Interesting discussion of performance of the two models can be found, for example, in [42]. A short comment on single-particle spectra calculated in selected Skyrme and RMF models is made in Sec.…”

Structural properties and decay modes of Z = 122, 120 and 118 superheavy nuclei

“…Prediction of decay modes, decay products, Q-values and half lives are very much crucial to probe superheavy nuclei, and knowledge of these properties is essential for the detection of these superheavy nuclei in laboratory. 5,7,[14][15][16][17][18][19][20][21] Here we present a systematic study of the decay properties of superheavy nuclei by calculating the α-decay and spontaneous fission half-lives of Z = 122, 120 and 118 isotopes within the range of A = 284 − 352 using RMF+BCS and NSM approaches. We have also calculated Q-values and log 10 T α for the decay chains of superheavy nuclei 294 118, 294 117 and 293 117, which have already been synthesized and their α-decay chains have been reported, 11 to validate our theories.…”

“…[2][3][4] Some efforts have already been made in nuclei with Z = 118, 119, 120. [5][6][7] The search for the possible fusion reactions with the help of available theoretical data on the distinct features and predictions has been going on at GSI, 8,9 RIKEN 10 and JINR [11][12][13] that are expected to provide useful information in this domain of periodic chart. Various theoretical attempts, [14][15][16][17][18][19][20][21][22][23] in particular, the studies of Z = 118, 24 Z = 118−121, 25 36 have significantly contributed to the knowledge of this unexplored region of nuclear landscape.…”

“…Various theoretical attempts, [14][15][16][17][18][19][20][21][22][23] in particular, the studies of Z = 118, 24 Z = 118−121, 25 36 have significantly contributed to the knowledge of this unexplored region of nuclear landscape. In addition, possible new shell closures, [37][38][39][40][41][42][43][44] the exotic phenomenon of bubble/semi-bubble structures [45][46][47][48] and the possible decay modes 5,7,[14][15][16][17][18][19][20][21]49 are being anticipated in this superheavy region which makes the study of this region very interesting that might open up new avenues for nuclear physics research.…”