Slow fission of highly excited plutonium nuclei

作者: AK Sikdar , A Ray , Deepak Pandit , B Dey , Sarmishtha Bhattacharyya

DOI: 10.1103/PHYSREVC.98.024615

关键词: Energy (signal processing)FissionPhysicsFull width at half maximumExcited stateCrystalAtomic physicsNuclear reactionLine (formation)Multiplicity (mathematics)

摘要: Background: Earlier measurements of fission lifetimes the highly excited uraniumlike nuclei by K x-ray fluorescence and crystal blocking techniques obtained slow (fission time $\ensuremath{\sim}{10}^{\ensuremath{-}18}\phantom{\rule{0.16em}{0ex}}\mathrm{s}$) for most events were shown to be incompatible with very short ($\ensuremath{\sim}{10}^{\ensuremath{-}20}\phantom{\rule{0.16em}{0ex}}\mathrm{s}$) nuclear also small (\ensuremath{\le}5%) percentage such predicted simple statistical models. One weakness earlier experiments is that observed peaks broad [full width at half maximum $(\mathrm{FWHM})\ensuremath{\approx}15\phantom{\rule{0.16em}{0ex}}\mathrm{keV}$] precise energies relevant lines could not determined from measurements.Purpose: The purpose look energy region in coincidence fragments a high resolution (\ensuremath{\approx}1 keV) spectrometer obtain evidence determine its percentage.Method: Highly plutonium produced fusion $^{4}\mathrm{He}+^{238}\mathrm{U}$ $E{(^{4}\mathrm{He})}_{\mathrm{Lab}}=60\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$. intrinsic was as direct measure (or lower limit) ($\ensuremath{\sim}{10}^{\ensuremath{-}18}\phantom{\rule{0.16em}{0ex}}\mathrm{s}$) events. minimum has been multiplicity per event probability creation K-orbital vacancies plutonium.Results: A narrow peak (FWHM \ensuremath{\approx} 1 photon spectrum (102.8 \ifmmode\pm\else\textpm\fi{} 0.5) keV, just below characteristic ${K}_{\ensuremath{\alpha}1}$ line (103.7 attributed on basis supporting calculations we deduce are $g{10}^{\ensuremath{-}18}\phantom{\rule{0.16em}{0ex}}\mathrm{s}$). No exactly 103.7 keV.Conclusions: shift [(0.9 keV] plausible, if fissioning nucleus spends long deformed dumbbell shape (beyond saddle) corresponding results agreement those atomic techniques. Alternatively, no significant can expected, absence keV contradicts technique claims

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