Yields of correlated fragment pairs in spontaneous fission of {sup 252}Cf
- Joint Institute for Nuclear Research, Dubna 141980 (Russia)
- Department of Physics, Vanderbilt University, Nashville, Tennessee 37235 (United States)
- Department of Physics, Mississippi State University, Mississippi State, Mississippi 39762 (United States)
- Institute of Physics, Slovak Academy of Sciences, Bratislava (Slovak Republic)
- Idaho National Engineering Laboratory, Idaho Falls, Idaho 83415 (United States)
- Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
Independent yields of 139 individual secondary fragment pairs of five different charge splits (Z{sub L}/Z{sub H}=46/52, 44/54, 42/56, 40/58, and 38/60) have been measured by detecting the coincidences between prompt {gamma} rays emitted in the spontaneous fission of {sup 252}Cf. Nuclear charge and mass distributions of fission fragments that follow from the measured yields of individual fragment pairs are consistent with similar previously known more integral data. Another type of data extracted is the multiplicity distributions of prompt neutrons emitted in the five above charge divisions of {sup 252}Cf. About 70{percent} of the fission events where {ge}7 neutrons are evaporated from the fission fragments occur for the Mo-Ba split of {sup 252}Cf. Mass and excitation energy distributions of primary Ru-Xe, Mo-Ba, and Zr-Ce fragments were deduced from a least squares fit to the yield pattern of secondary fragment pairs. For the Ru-Xe and Zr-Ce splits, the experimental data are well fitted by assuming one fission mode with average total kinetic energy {l_angle}TKE{r_angle} values close to the value of {l_angle}TKE{r_angle} known for the {sup 252}Cf spontaneous fission. For the Mo-Ba split, a successful fit could be obtained only with the assumption that, in addition to this {open_quotes}normal{close_quotes} fission mode, a second mode with a remarkably lower value of {l_angle}TKE{r_angle} of 153 MeV contributes to this charge split. This is 36 MeV lower than for the normal mode. These data indicate that in mode two the barium nuclei are hyperdeformed (3:1 axis ratio) at scission. Mean angular momentum values of Mo-Ba fission fragments observed in pairs together with various partners have been deduced from the measured populations of different spin levels of the fragment nuclei. These angular momentum values are discussed in terms of their dependence on the primary fragment excitation energy and presence of two fission modes. (Abstract Truncated)
- Research Organization:
- Oak Ridge National Laboratory
- DOE Contract Number:
- AC05-84OR21400; AC07-76ID01570; FG02-88ER40407
- OSTI ID:
- 524963
- Journal Information:
- Physical Review, C, Journal Name: Physical Review, C Journal Issue: 3 Vol. 55; ISSN 0556-2813; ISSN PRVCAN
- Country of Publication:
- United States
- Language:
- English
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