Fission and binary fragmentation reactions in {sup 80}Se+{sup 208}Pb and {sup 80}Se+{sup 232}Th systems

Journal Article · Thu Feb 15 00:00:00 EST 2007 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.75.024604· OSTI ID:20991017

Thomas, R G; Saxena, A; Sahu, P K; Kailas, S; Kapoor, S S ^[1]; Choudhury, R K ^[1]; Govil, I M ^[2]; Barbui, M; Cinausero, M; Prete, G; Rizzi, V ^[3]; Fabris, D; Lunardon, M; Moretto, S; Viesti, G; Nebbia, G; Pesente, S ^[4]; Dalena, B; D'Erasmo, G; Fiore, E M ^[5]

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1. Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)
2. Department of Physics, Punjab University, Chandigarh 160014 (India)
3. INFN Laboratori Nazionali di Legnaro, I-35020 Legnaro (Pd) (Italy)
4. Dipartimento di Fisica and Sezione INFN Padova, I-35131 Padova (Italy)
5. Dipartimento Interuniversitario di Fisica and Sezione INFN Bari, I-70100 Bari (Italy)

Fission and binary fragmentation of the excited nuclear systems of Z=116 and 124 were investigated using the reactions induced by {sup 80}Se beams on {sup 208}Pb and {sup 232}Th targets at bombarding energies ranging from 470 to 630 MeV. The mass and kinetic energy of the binary reaction products were reconstructed by measuring their velocities by the time-of-flight method and the angles of emission using multiwire proportional chambers. Total neutron multiplicities were measured in coincidence with the fragments, using an array of neutron detectors. The fragment mass-energy correlation was studied for the two systems. The average total kinetic energy (TKE) of fragments for the {sup 80}Se+{sup 208}Pb system agrees with earlier measurements and with Viola's systematics in the mass symmetric region for compound nucleus fission, whereas for the {sup 80}Se+{sup 232}Th system, the TKE values are significantly lower. This is also consistent with higher values of total neutron multiplicities observed for the case of {sup 80}Se+{sup 232}Th at comparable available energies. From an extrapolation of the measured total neutron multiplicities for the mass symmetric region to zero compound nucleus excitation energy, the average number of prompt neutrons expected to be emitted in the spontaneous fission of the superheavy Z=116 has been estimated to be {nu}{sub tot}{sup sf}=10{+-}2, which is consistent with the value derived for the same compound nucleus populated in the {sup 56}Fe+{sup 232}Th reaction in an earlier work. In the case of the {sup 80}Se+{sup 232}Th system, similar analysis was carried out by taking the average TKE from Viola's systematics for estimating the available energy for particle emission corresponding to compound nucleus fission. In this way, by extrapolating the observed neutron multiplicities to zero compound nucleus excitation energy, a value of {nu}{sub tot}{sup sf}=15{+-}2 was obtained for the spontaneous fission of the superheavy Z=124 nucleus. The increase in the average number of neutrons emitted in fission as a function of the atomic number of the nucleus in the superheavy mass region was confirmed by comparing the results of the present work with published data.

• OSTI ID: 20991017
• Journal Information: Physical Review. C, Nuclear Physics, Vol. 75, Issue 2; Other Information: DOI: 10.1103/PhysRevC.75.024604; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
COMPOUND NUCLEI
EMISSION
EXCITATION
EXTRAPOLATION
FRAGMENTATION
IRON 56
KINETIC ENERGY
LEAD 208
MASS
MEV RANGE 100-1000
MULTIPLICITY
MULTIWIRE PROPORTIONAL CHAMBERS
NEUTRON DETECTORS
PROMPT NEUTRONS
SELENIUM 80
SPONTANEOUS FISSION
THORIUM 232
TIME-OF-FLIGHT METHOD