Статья

Fission time scale and viscosity for compound nucleus<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow/><mml:mrow><mml:mn>220</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi mathvariant="normal">Th</mml:mi></mml:math>formed in reaction<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow/><mml:mrow><mml:mn>40</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">A</mml:mi><mml:mi mathvariant="normal">r</mml:mi><mml:mo>+</mml:mo></mml:mrow><mml:mrow><mml:mn>180</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi mathvariant="normal">Hf</mml:mi></mml:math>at<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>E</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">lab</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mo>=</mml:mo><mml:mn>180</mml:mn><mml:mo>,</mml:mo></mml:math>190, 216, and 249 MeV

V. A. RubchenyaDepartment of Physics, University of Jyväskylä, FIN-40351, Jyväskylä, FinlandAndrey KuznetsovDepartment of Physics, University of Jyväskylä, FIN-40351, Jyväskylä, FinlandW. H. TrzaskaDepartment of Physics, University of Jyväskylä, FIN-40351, Jyväskylä, FinlandД. Н. ВахтинDepartment of Physics, University of Jyväskylä, FIN-40351, Jyväskylä, FinlandA. A. AlexandrovFlerov Laboratory of Nuclear Reactions, 149980, Dubna, RussiaI. D. AlkhazovV.G. Khlopin Radium Institute, 194021, St. Petersburg, RussiaJ. ÄystöDepartment of Physics, University of Jyväskylä, FIN-40351, Jyväskylä, FinlandS. V. KhlebnikovV.G. Khlopin Radium Institute, 194021, St. Petersburg, RussiaV. G. LyapinV.G. Khlopin Radium Institute, 194021, St. Petersburg, RussiaO. I. OsetrovV.G. Khlopin Radium Institute, 194021, St. Petersburg, RussiaYu. É. PenionzhkevichFlerov Laboratory of Nuclear Reactions, 149980, Dubna, RussiaYu. V. PyatkovFlerov Laboratory of Nuclear Reactions, 149980, Dubna, RussiaG. P. TiourinV.G. Khlopin Radium Institute, 194021, St. Petersburg, Russia

1998lv

ABI

Аннотация

Double differential spectra of neutrons emitted from the reaction ${}^{40}{\mathrm{A}\mathrm{r}+}^{180}\mathrm{Hf}$ at ${E}_{\mathrm{lab}}=180,$ 190, 216, and 249 MeV were measured in coincidence with fission fragments using a multidetector array. Averaged prescission and postscission neutron multiplicites were extracted from the spectra together with temperature parameters. These values were analyzed in the framework of a modified version of the statistical model with inclusion of dynamical hindrance of fission, which depends on nuclear dissipation. From comparison of the experimental and calculated neutron multiplicities and temperatures it was deduced that nuclear viscosity is strong at excitation energies higher than $\ensuremath{\sim}40\mathrm{MeV}$ and decreases with the decrease of excitation energy during evaporation cascade. The extracted fission time scale changes from $40\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}\mathrm{s}$ to $17\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}\mathrm{s}$ in the investigated projectile energy interval.

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Идентификаторы

DOI: 10.1103/physrevc.58.1587

Цитирования и источники

Цитирований: 2Использованных источников: 0

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