The dependence of fission time-scales on fragment mass asymmetry in the 20Ne+165Ho reaction at 50A MeV |
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| Institution: | 1. Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA;2. Institute of Physics, Jagellonian University, ul. Reymonta 4, 30–059 Kraków, Poland;1. Physics Department, Faculty of Science, Cairo University, Egypt;2. Physics Department, Zewail City of Science and Technology, Egypt;1. School of Physics and Materials Science, Thapar Institute of Engineering and Technology (TIET), Patiala-147004, Punjab, India;2. Department of Physics, University Institute of Sciences, Chandigarh University Gharuan, Mohali-140413, Punjab, India;1. Institute of Transportation Systems Science and Engineering, Beijing Jiaotong University, Beijing 100044, China;2. IceLab, Department of Physics, Umeå University, 901 87 Umeå, Sweden;1. Institute of Nuclear Chemistry, Johannes Gutenberg University Mainz, 55099 Mainz, Germany;2. GSI Helmholtz Centre for Heavy-Ion Research, 64291 Darmstadt, Germany;3. Helmholtz Institute Mainz, 55099 Mainz, Germany;4. Advanced Science Research Center, JAEA, Tokai-mura, Ibaraki 319-1195, Japan;5. Lawrence Livermore National Laboratory, Livermore, CA 94550, USA |
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| Abstract: | The pre-scission and post-scission multiplicities of alpha particles were determined in coincidence with fission fragments for four windows of exit channel mass asymmetry in the reaction 20Ne+165Ho at 50A MeV. The technique used employed a kinematic analysis of the energy spectra of alpha particles as a function of the emission angle with respect to the fission axis. Using a procedure of fitting the experimental energy spectra with those resulting from a Monte Carlo simulation program, the total multiplicity of alpha particles was separated into pre-scission and post-scission components. Using the pre-scission and post-scission multiplicities, neutron multiplicity measurements and other empirical observations, both the initial excitation energy and the excitation energy at scission of the compound nucleus were determined. The pre-scission times in the de-excitation of a highly excited 178W compound nucleus with initial excition energy of 570 MeV were evaluated using statistical model calculations. Only a small decrease in scission time was derived for the most asymmetric events studied. The possible contribution of very damped deep inelastic processes is discussed. |
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