Observation of Delayed Nuclear Fission in the Region of¹⁸⁰Hg

Abstract

PACS. 25.85. -Fission reactions. PACS. 23.40. -Beta decay; electron and muon capture. PACS. 27.70. -150 d A d 189.

β-delayed fission of180Tl

“…The obtained σ ( 180 Tl) was in the range of several μb, which is ∼100-1000 times lower than the value estimated in Ref. [14]. If one now uses our cross-section estimate instead of 0.1-1 mb, used by Lazarev et al, the P βDF ( 180 Tl) value from Ref.…”

“…The TKE spectrum, determined by summing up the energies of coincident fragments is shown in Fig. 5, which established the most probable TKE of 133.2 (14) MeV with a FWHM = 15.0(9) MeV. It is interesting to note that the FWHM values obtained for the fission of 180 Hg are substantially smaller compared to those obtained from spontaneously fissioning nuclei in the heavy mass region (around 252 Cf), which are above 23 MeV [1].…”

“…It was deduced from the ratio of the measured fission cross section and estimated production cross section of σ ( 180 Tl) ∼ 0.1-1 mb in the reaction 40 Ca + 144 Sm → 180 Tl + p3n; see also Ref. [14]. The latter rough estimate was made by the authors of Ref.…”

“…This decay mode will happen in competition with γ and/or particle (neutron or proton) decay. So far, this process was observed in only a dozen of very neutron-deficient nuclei in the transuranium region [8] and a few nuclei in the lead region [14][15][16][17], and in the neutron-rich region several cases of βDF are known [18]. The most recent review of βDF is given in Ref.…”

β-delayed fission of192,194At

“…First experiments in the lead region were performed by Lazarev et al [9,10]b yu s i n g complete-fusion reactions induced by heavy ions, and three βDF candidates were identified: 180 Tl, 188 Bi,and 196 At. Due to the use of mica detectors and a relatively simple production and identification method, only the fact of fission itself and the half-life value of the fissioning candidate nucleus could be deduced in these experiments.…”