Nuclear fission induced by radiationless transitions in the MU-mesonic atoms Th232, U235 and U238

Abstract

The time distributicn of fissions in Th 232 , u 235 , and u 238 induced by ._., • mesons was measured with a multipla.te gas-scintillation fission chamber. A significant number of prompt fissions *-ot associated with~.~.nuclear. .. capture was:.'~ observed. The results are: Nucleus. • .Ratio of prompt fia sions to fissions from nuclear capture o.o64 :J: .ozz 0.072 d: .014 0.111 :!': .021 The work of Mukhin et al,. shows tbat the intensities of tJ.•mesic K x-ra.ys. '. ,. ' for these elements relative to Pb are o.ss :!:: .• 0 (Th), o. 77 ± .04 (u 238), and. .. r. 235 0.11 :t: ,OS (U). This intensity reduction is qualitatively consistent with earlier predictions that, for these elements, a direct excitation oi the nucleus competes with electromagnetic radiation in the transition to the ground state of '. the mesic atom. Our results indicate such direct nuclear excitation. The number of fissions observed may be. consistent with the results o! • Mukhin et al. and with photofission data. i£ allowance is made for the effect 011 the fission barrier o£ the ._.,meson in the lS state of the mesic atom.

The probability of prompt and delayed fission of muonic237Np

“…(2p-~ ls)-and (3d--,ls)-transitions in several muonic actinide nuclei, and of their respective fission probabilities. The energies of the barriers of fissile actinides are comparable to the energies of the muonic K s X-rays, while the fissility varies strongly from Th to Pu [5,[9][10][11]. Experimentally, there is a systematic and rapid increase of the probability of prompt fission with the value of the fissility parameter [9][10][11].…”

Muon-induced fission in 235U and 238U

“…The 4~o evidence was found for a second component with T' = 18 * fitting function consisted of a prompt component, one or two 5 ns (intensity 8 * 2%) as was required in fitting our previous data (9 (2,8,(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) are summarized in Table 3.…”

The study of prompt and delayed muon induced fission

“…A negative muon which cascades down in an atom of a heavy element may induce fission by two distinctly different processes [1][2][3][4][5][6][7][8].…”